Sorry this took me so long to respond. I only saw the post right now.
@nim6us you are right on in your assumption. When mixing the AFR Powder, you want to mix 160g (I think that is 6 level scoops) into RO/DI water to result in a full 1000 ml solution. We recommend starting with about 900 ml of RO/DI water (it makes it easier to dissolve the powder) and then add as much is needed. It is almost always about an additional 50 ml that is needed. That means that you can also start with 950 ml of RO/DI water, if you would like, and you will almost always end up right on the full 1000 ml solution.
It is also true, however as
@Randy Holmes-Farley said, that it doesn't make very much difference. As you can see it is only a matter of about 50 ml one way or the other. This makes very little difference in the concentration of the final solution. That would be true even if you started with the full 1000 ml of RO/DI water, you would only end up with about 1050 ml of final solution.
But for us OCD types, the 900 ml and topping off after dissolving is the best way to go and bee 100% accurate.