to BP.net...
When you get the thermostat, the probe should go under the tank, between the UTH and glass to keep it from getting urine and feces on it. What I do is use a piece of aluminum tape across the probe cord to hold it in place and keep it from sliding out. Then just position the UTH and tape it down. I don't really remember, but I think the ReptiTemp500r doesn't have numbered degrees. It has color bands like green, yellow and red. Maybe someone who uses one can either confirm or deny this for me. Basically the way you set it up is turn it on low and wait a while for the temps to stabilize and then check it. Then about every 20-30 minutes bump it up a little more until you get the desired temp.
One other thing that can help cause excessively high temps on the glass is if you are using a thick layer of substrate. What are you using? and how thick is it?