It’s from the manual for the infrared reading device I use. You can set it on body or surface mode. In surface mode it is just like a Harbor Freight sensor. In body mode you are supposed to read your forehead temp. It compensates that surface reading to give you a body temp.
Let me do a test.
Body setting forehead temp - 97.9 F
Surface setting forehead temp - 91.9 F
Wow. Major compensation.
Oh, no wonder.