the weights go in 2 gram increments. They depend on what swing weight you are looking for and if you are lengthening or shortening the club. 0.5" shorter is +2 grams for standard weight, 0.5" longer is -2g.
if they add or subtract 2g it will be from the lighter 3g weight. if it's +/- 4g it will be 2 from the lighter and 2 from the heavier weight

I.E. I ordered a club 0.5" shorter and they put a 5g weight and 11g weight. -4 and +2 from standard (9g)

Assuming you bought off the rack you’ll have a 3g and an 11g weight. If the heavier one is nearer the face it’ll cause the driver to present less dynamic loft at impact than if it were at the back. This causes lower spin and launch angles and generally lower peak height than if the heavier weight were set in the back.

Your best bet is to go to a good club fitter to work through what will best suit your needs. Especially if you need to adjust the length of your driver, or want to put on an unusually heavy grip which will affect swing weight, and you might need to order different combinations of weights to keep the driver well balanced for you.