Mr. Mack: What does the book say? The owners manual says to keep the lights 1 to 2 inches above the tops of your plants but when they sprout you can't get them that low so the very bottom setting on the arm/light stand encourages your seedlings to grow up to the lights. If you don't have the book, everything in it is on line for you to review and if you're asking questions like that it's time to RTFB because things are going to start happening fast. For the sake of your babies I hope that helps. HSA