In theory the math you have given is correct.
However - it is practically impossible to actually do so.
Any time you perform a compounding function, there will be some loss of drug. As some of the powder will stick to every implement you manipulate it with. Similar to in chemistry, you never get 100% of your reagents to react the way you want to. It is an imperfect world, so if you get 2000 tablets out of that, some will be underweight.
Further, most pharmacies do not have equipment to prepare actual tablets. Tablets can be crushed, their volume expanded (as you would need to do and this case) and hand packaged in individually weighted capsules.
