Not much I can add here, but generally 7 gram increments is the norm. TaylorMade, and all manufacturers for that matter, will have specific head weights and progressions of weights based on the stock standard build they are doing. Grip weights and shaft balance point and weights are all taken into consideration. Most tolerances on head weights are the +2.5-3g and munus 2.5-3g. Not unusual to get one that is a little over and the next one a little under, resulting in what you have. You have to work up to the heaviest weight of the two, unless you want to counter balance the heavier or have the ability to reduce the weight of the head, which you can’t really do on that head.