That is the weight attached to the bottom of the clubhead. Specs recommend plus 2 gram weight over standard. Not uncommon.

Like Barry said, not uncommon. The GT1 head is lighter which helps speed up the swing for slow swingers but the downside can be a lack of feel of the clubhead. Some people (including me) use heavier weights in the head to increase feel in the swing. I can better square up a heavier head. Trick is not to go so heavy that it slows your swing speed. That’s what your fitter has done, sign that you got a good fitter as some spend all the time on head and shaft combinations and not so much the weight variations. Enjoy the new driver!

If you want numbers, the standard head weight on a GT1 Driver is 9 g. +2 means you have an 11 g weight.

Hi, John B has the right answer.
The fitter probably did this to arrive to a specific swing weight in accordance with the specific shaft.
He took in consideration the weight, length, grip etc..