We had a Honeywell CT87N round thermostat installed. The heat comes on but the actual temp on the bottom stays much lower - like 8 degrees lower. Is there a way to calibrate the thermostat so that they match?

One thing you can try is to remove cover, it just snaps in place.There are two plastic leveling posts at top two sides. You will need a small level commonly called a torpedo level to set on these leveling points.It should be very close to level,bubble in middle. If it's not look at base plate against wall and locate two lower mounting screws there will be a small slot where the screws go into wall to allow for slight adjustment.You will need a small screwdriver to back these two screws out a little maybe 1 turn.Adjust thermostat base so that level has bubble in middle and carefully tighten the screws,keeping t-stat held level. This should help some but it is not unusual for set temp. ont-stat to be off 3-5 degrees from thermometer reading. Hope this helps you.Thanks.