According to my observation, there are at least two types of using "Not that....". And my question is: what does "not that" mean in its second type of usage.

In the first usage, "not that" is followed by a structure-complete sentence or expression.

Example 1

I've been teetering down my twittering and self editing my Facebooking lately. It's not that I don't have the urge to write things. It's just I have to fight the urge to write really inappropriate things that maybe my old High School English teacher doesn't really need or want to know.

Example 2

It’s not that I don’t care about football. I just don’t care enough

In the second usage, "not that" is followed by a object-missing expressions.

Example 3(from Fringe)

Olivia: Anything to do with metamorphic ability? Peter: Not that I can tell

Here, "tell" is a transitive verb and its object is missing.

Example 4 (from Fringe)

Olivia: Were you involved in...? Walter: Not that I recall

Here, recall is a transitive verb and its object is missing.

**I understand that, in the first usage, "not that" sort of means "it doesn't mean...". But I'm not sure, in the second usage:

1. why objects of transitive verbs are missing?
2. what do this type of "not that..." sentences mean here?**

According to my observation, there are at least two types of using "Not that....". And my question is: what does "not that" mean in its second type of usage?

In the first usage, "not that" is followed by a structure-complete sentence or expression.

Example 1:

I've been teetering down my twittering and self editing my Facebooking lately. It's not that I don't have the urge to write things. It's just I have to fight the urge to write really inappropriate things that maybe my old High School English teacher doesn't really need or want to know.

Example 2:

It’s not that I don’t care about football. I just don’t care enough.

In the second usage, "not that" is followed by an object-missing expression.

Example 3  (from Fringe):

Olivia: Anything to do with metamorphic ability? Peter: Not that I can tell.

Here, tell is a transitive verb and its object is missing.

Example 4 (from Fringe):

Olivia: Were you involved in...? Walter: Not that I recall.

Here, recall is a transitive verb and its object is missing.

I understand that, in the first usage, "not that" sort of means "it doesn't mean...". But I'm not sure, in the second usage:

1. Why are objects of transitive verbs missing?
2. What does this type of "not that..." sentences mean here?

There seems to be at least two types of using "Not that....". And my question is: what does "not that" mean in its second type of usage.

In the first type, "not that" is followed by a structure-complete sentence or expression.

Example 1

I've been teetering down my twittering and self editing my Facebooking lately. It's not that I don't have the urge to write things. It's just I have to fight the urge to write really inappropriate things that maybe my old High School English teacher doesn't really need or want to know.

Example 2

It’s not that I don’t care about football. I just don’t care enough

In the second type, "not that" is followed by a object-missing expression.

Example 3(from Fringe)

Olivia: Anything to do with metamorphic ability? Peter: Not that I can tell

Here, tell is a transitive verb and its object is missing.

Example 4 (from Fringe)

Olivia: Were you involved in...? Walter: Not that I recall

Here, recall is a transitive verb and its object is missing.

I understand that, in the first type, "not that" sort of means "it doesn't mean...". But I'm not sure about the second usage, and I don't understand why the objects of the transitive verbs are missing

According to my observation, there are at least two types of using "Not that....". And my question is: what does "not that" mean in its second type of usage.

In the first usage, "not that" is followed by a structure-complete sentence or expression.

Example 1

I've been teetering down my twittering and self editing my Facebooking lately. It's not that I don't have the urge to write things. It's just I have to fight the urge to write really inappropriate things that maybe my old High School English teacher doesn't really need or want to know.

Example 2

It’s not that I don’t care about football. I just don’t care enough

In the second usage, "not that" is followed by a object-missing expressions.

Example 3(from Fringe)

Olivia: Anything to do with metamorphic ability? Peter: Not that I can tell

Here, "tell" is a transitive verb and its object is missing.

Example 4 (from Fringe)

Olivia: Were you involved in...? Walter: Not that I recall

Here, recall is a transitive verb and its object is missing.

**I understand that, in the first usage, "not that" sort of means "it doesn't mean...". But I'm not sure, in the second usage:

1. why objects of transitive verbs are missing?
2. what do this type of "not that..." sentences mean here?**