@RobPNW correct. So if you tell the Teric that your setpoint is 1.1, then in order for it to actually give you some sort of useful deco information, you have to maintain a setpoint of 1.1. Doesn't have to be exact but you want say 1.05:1.15 which is a lot less difficult than it sounds.
The diver monitors the actual parameters via something that is attached to the computer. All of the breathers on the market now, to my knowledge have integrated decompression computers that are actively monitoring the cells, so they monitor in real-time, with real ppO2 data. Back in the day, they would just be monitors and you had to keep your ppO2 close enough to whatever value you told the computer.