1.00 = 1 G

0.10 = 100 MG

0.01 = 10 MG

0.001 = 1 MG

I agree with everyone else definitely look into your smoking method/purity of extract. Also maybe check your scale calibration put a nickel on it the nickel should weigh 5 Grams even, depending on the side of the coin... (yes sometimes this matters) it might be 4.9 or 5.1 but this is ok for a nickel... as some scales can be off by this amount as listed in their instructions. You may also have a really cheap scale that says it can read to a 100th of a gram but might not be doing so accuretly. A chunk of about 50 MG DMT should be more than sufficient for a breakthrough for most people. And 50 MG should be loosely powdered to roughly the size of a new pencil eraser, but never try to eyeball MG sensitive doses. Best bet though is if you can't measure properly to just add the 100MG that you've been adding and smoke it by counting hits as others suggest in other threads, And make sure you hold your hits as long as possible.

And to answer how many hits per gram assuming you used 50 MG perfectly every time you smoked and never wasted any that should equate to 20 Full breakthrough doses per gram based on assumption of decent purity/smoking technique and your personal tolerance.