With the error rate of hydrofarm and the error rate of a typical digital 10º difference is not out of possibility. The problem with hydrofarms is the if it is working correctly you could set it at 90 and it could actually be from 86-94º. Add swing, regular thermometer error and you can easily double this. As I stated earlier that it is likely both hydrofarm and thermometer that are off one one direction one the other.

The truth is that helix herpstat ecozone herpkeeper and VE all have accuracy of less than 1ºF these are actually cheap accurate thermometers the fact is is also a great thermostat is just a bonus.

When you have no way of knowing what is right you have no way of knowing what is wrong.