Does the term 'at most' mean there is at least one?
"at most one"
one or less.
The free dictionary points out that at most can be replaced by "not more than".
In which case
- at most one can be equated to not more than one,
- at least one means not less than one.
It means "no more than one." Many times it is used to imply "no more than one, if even that."