The 4ad at 1fast400 says that the Amount per 1/4 tsp:
is 300mg but how many tsp are in 1 gram? is it 1?
A teaspoon is not accurite enough though! Get some scales
.83... tsp would be 1 gram. You can go with 3/4 of a tsp for 900mg.
If you want to stick with spoons for this and other things, Ecko sells a spoon set called a "Dash, Pinch and Smidgen" for cooking, avaliable at places like Walmart for a few $. I've scale measured the amount each holds, the dash is very close to 1/6 tsp, the Pinch at 1/12 and the smidgen at 1/24, you can mix and match various spoon quantities to get pretty good accuracy.