na dude check out the box again it should say for indoor plants to use 1/2 teaspoon per gallon of water. The small end of the spoon. Go by that, that's what I went by to start with and I've never burned my plants (badly). Let them build up a tolerance to it. Now I give them 3 teaspoons per gallon every other watering until the start to show signs of burn (just slightly browning on tips or edges of fan leaves) then i give 'em 2 water only waterings and the are growing pretty good. That's the very best method I've come up for MG feeding through trial and error.
Oh and remember to only feed or water them when the soil is dry to the bottom of their roots (guesstimate) especially when they're seedlings you want their roots stretching out for that water. The reason you wanna let the soil dry out is because you want the plant to think it's in a drought and start to produce resin to protect itself.
Happy Growing!!
PS trust me on this