WDTC-20 oddity - temp always 5 off?

I just got a WDTC-20 and in Vera i see

Current Temp: 73
Set point Heat: 70
Set point Cool: 65

however the current temp on the actual device is 78
cool set point is 70 and heat is 75

All the vera readings are 5 lower than the real readings. Any reason for this?

Thank you