There's many teks in our WIKI, click my signature, go to 'extraction teks', check the A/B ones, they should tell you how much water to use.
The solubility of pure DMT in acidified water is not the same as the solubility of DMT mixed in with a lot of other plant "impurities" that will be present in a brew, so it wouldnt really be possible to answer your question. But DMT extractions are very forgiving, you dont need to be exact. Just be sure not to throw anything away before you have your final yield, that way if something goes wrong you can always go back and recover.