Maybe you have an older bottle and it doesn't say that though. A level teaspoon is 5 grams. And I know you didn't ask, but I think Swole by Syntrax is a much better product.
The reason TRAC says 16g instead of 5gs is because TRAC is more thn creatine. TRAC also contains L-Arginine, NADH and dextrose, sucralose, folic acid and a bunch of other stuff.