Ppm

I need a little help.....rdwc 2 plant set up.....ok to my question. Let's say my feeding schedule says 500ppm, my meter has a .5 and .7 setting I think, so which one of these settings do I use.....if one says 500 the other is different and I'm confused......I understand the ec I just want to know which ppm setting I'm supposed to use, thanks for helping a noob

what is your feeding schedule based on , .5 or .7?

that's why people should only use EC. no confusion.