After trusting the oven’s temperature display, I got an inexpensive digital thermometer to verify its readings. I always seal flower in aluminum foil to reduce loss of volatile terpenes, and place it on a dish in the oven.
The oven’s thermometer was reading about 20 ° F higher than the actual temp of the remote one. So I was under-decarboxylating by about 10%, due to the insulating effects of a plate, aluminum foil and herb.
Bottom line is that you can’t really trust a digital oven thermometer to be accurate enough for complete conversion of THCA to THC. (THCA does have medical benefits of its own and it isn’t psychoactive)