The natural way to read it is as SchroedingersCat already mentioned. But this does also works if the pairs were mixed:
(GN3001 and BC3006) or (GN3002 and BC3007)
It has nothing to do with similar IDs for units, it's just a question of how the man's brains works. It isn't important what the numbers are, another example
AA1001 and BB2002 or CC3003 and DD4004
is also read like the first example above:
(AA1001 and BB2002) or (CC3003 and DD4004)
This construction is the simplest way how to structure them and thus this is the way our brain/mind works.
Think of the alternatives:
- AA1001 and (BB2002 or CC3003) and DD4004
- AA1001 and (BB2002 or (CC3003 and DD4004))
Even with parenthesis it's not that easy to read. The first alternative interpretation is unlikely, because it does absolutely not fit our brain's/mind's structure. If you wanted to intend that one you ever have to clarify it.
The latter would only concur with our mind structure if you know that the value, performance, ... of BB2002 is greater than or equal to CC3003 and DD4004 together. Though, it is only secondary in our mind, because the logic behind it is also much more complicated.
Thus, in a nutshell, you first connect the both "and"-condition and then choose either of them as the "or"-condition requires.