Here is my math;
We are talking about level teaspoons. My spoon fitted exactly 1 gram of borax, level that is.
1/8 of that is 125 mg borax, of which is 11 % boron = 13,75 mg of boron.
I have taken 1/4 for years (2-3 days a week) The workers in the borax mines inhale around 30 mg of boron daily via the borax dust. This was a study about it, no adverse effect found.