Hi, that is the indication for "Error" and you should first replace the (2) AA batteries in the thermostat, (even if you just replaced them recently) and then using a small paperclip, reset the thermostat, by inserting the unbent end of the paperclip into the reset hole next to the keypad.
Be advised that this will reset the thermostat to the default temperature and time cycle settings, so you'll have to reprogram the unit, once you've reset it. With your unit, you only need to set a weekday setting and one for each of the weekend days.
Here's a copy of the instructions for your use in resetting and reprogramming the thermostat, once you've replaced the batteries.
http://www.hunterfan.com/uploadedFiles/Support/Owner_Manuals/44260.pdf
You can also contact Hunter tech support, should the above info not get your thermostat back in working order by calling them at 1-888-830-1326, from 8 AM to 5 PM Central Time.
I hope you find this Very Helpful and best regards!