I recently set up my Hydrofarm thermostat and I'm not sure of the placement of the probe. Dose it need to be directly in the substrate or hanging above the substrate. I currently have it above Substrate next to my Accurite thermometer. There is about a 5 degree difference between my hydro temp and my Accurite temp. Not sure which is more accurate. I set my Hydrofarm to go off at 82. It is currently at 86.5 my Accurite is at 91. I'm not sure if i should lift my lamps or readjust my Hydrofarm temp.