It is a number 2 interval, but being 4 semitones, it is beyond an augmented second. So, what it is?
The interval from any G (flat / sharp / neutral) to any A (flat / sharp / neutral) (in the same octave) is always a second. In your case, since the G is flat and the A is sharp, you have a doubly augmented second.
Of course, this interval is sonically equivalent to a major third.