I have Natural gas BradfordWhite with a thermostat that looks something like this-

Notice the A,B,C settings. My question is am I able to put the settings in between the settings like in the middle of A&B?, or must the knob line up on the mark?

Are there detents at those positions? Does it “click” into those spots? If not I’d expect you’re good anywhere on the scale that yields the desired temperature at your faucets.

https://www.youtube.com/watch?v=XKy2o_tci9Q

Although SF often provides "the" answer, it is often a good idea to check youtube.

I missed it if that video answered his question.

Infinite setting, the labels are reference points.

You can put it in between. I have that same thermostat on my gas water heater, and have mine between B and C. (Roughly in the low 140s.)

Thanks all.

In the summer I kept it at A. I moved it to B when winter came, but it felt like a big jump in heat. I'll stick it in between A/B tomorrow and see how it is.