I've about 150 water left over.

But at the same time, I have donated almost 600 sets, so this isn't a significant deviation.

I also know for a fact that some member in my group need water, he just don't have much of what I need (we do trade to some extend, but cant resolve all of them)

vague ballpark numbers w/o context means nothing. If you want to prove a case, find out how many of each chakra the top 10 "feeder" of your group have as well as how many sets they have already fed. Calculate, from this, roughly how many chakra of each nature that your group have gotten as a whole, and then you will be able to see if the deviation is within expectations.