Depends on the size of the spoon. But around 40-60 mg, if a level teaspoon.
An easier way to measure is to fill a 00 sized capsule half full, that would give approx 40-50 mg. Take it with vit C, somehow they work well together. You will need at least this amount to get rid of major joint and muscle pain.
The chelated boron is probably made from borax, most boron supplements are.
10 pills would give some boron, but check them for other ingredients, like magnesiums stearate, calcium phosphate.
I always choose the purest form of supplements, the amino acids you can always take along side with it (chelation)
Others here take tri-boron, but I am not familiar with it.