200 grams of dry sift hash will render a lot of the good stuff. Typically, most dry sift hash can be around 50-60% THC depending on the strain and how it was processed, as well as how fine the screen(s) were, which also helps to determine the quality. Dry Sift Full Melt Hash can be as high as 75% THC. Unless you get it tested you are guessing to an extent. Maybe consider it to be 60% potency. You can assume there will be some loss when infusing, but in this example, we'll keep it simple where there is no loss of THC throughout the infusion process.
200 grams x 1000mg = 200,000 mgs of THC!!!
.60 x 200,000 = 120,000 milligrams to infuse into 500 milliliters of water (16.9 fluid ounces). With this in mind, you will have a rough (very rough) idea of how many MG's you will have in each serving.