According to http://www.cag.uconn.edu/NUTSCI/NUTSCI/outrch/pdf/HowMuchSaltSugar.pdf there is 2,000 milligrams of salt in one teaspoon of salt. Using algebra you can determine that there is .36 teaspoons in 720 milligrams of salt.
Add 1/4 tsp of salt almost 1/8 tsp of salt together. You could add the full 1/8 tsp of salt but you will have just a little bit more salt than you need. It's not a big difference.
1 mg of salt equals .00018 teaspoons, so 100 mg eguals 0.018 teaspoons of salt.
620 mg of salt is an eighth (1/8) of a teaspoon.
That is 260 teaspoons.
I think it is about 1-1/4 teaspoons
That is 1/5 of a teaspoon
That depends on the weight of the material in the teaspoon. Probably one or two teaspoons for salt, flour etc.
how many teaspoons of fenugreek seeds are equals 300 mg
5 teaspoons of water equal 25 mg.
That is 203 teaspoons.