Bests & Worsts Reviews from Amazon

Arrived quicker then expected. Set it up and gave it 24 hours to adjust. Set it on my home HVAC control along with a known accurate hydrometer. The hydrometer was just over 10% reading lower than it should. The temperature reading was anywhere from 3 to 2 and 1/2 degrees off. Try to send it back only to find out it's not returnable even though it's Amazon prime. Very frustrated with the fact that Amazon rates it as a prime item but then won't let you return it...???