didn't come with any kind of instructions... still not sure how/ if they are working, if I ever figure it out, I'm sure it'll be fine

Not sure that they are working. I've put all 4 of them into plants and watered the plants with water running out of the bottom of the pots and they don't move from minimum amount.

I would not recommend this product. The meter works in water but not once placed in soil. I over watered my plants, water was all over my wooden floors(so sad) and the meter never moved. I tried the meter in glass of water and it worked but again not in soil.