Can you refer to the source that talks about that? It's quite a big deal if that little extra grams of SN ensures more chances of CTB from 68% to 100% (obv not literally). I myself am about 105kg/232lbs and thought of using 30g of SN. But using the calculation you indicated, from what I understand, it's less likely to succeed than using (180 * 2 * 105) / 1000 = 38g of SN. I'm almost a perfectionist on this because I really wanna make sure than when I attempt that one time, it won't backfire
The idea is that it will be soluble and dissolved when consumed. They say technically you want to use as little water as possible, it should be just enough where it can be consumed like liquid in your mouth, and about 2mL per 1g of SN, so if you use 30g of SN, you should use 60 mL of water. The range they mention for 25g of SN is between 50mL - 100mL, but it won't be overkill if you had just that little more mL, more important to get the right SN amount imo