Are they ok with it, if they know?
Totally hypothetical situation, of course. Let's say that you've been with more people than your SO. You've only been with <10 people.* But it bothers them because they see that number as a lot, and they happen to know a few of the people you've slept with. Imagining you with them is repulsive to your SO. How would you react to this situation?
* ETA: you got STD tests after each person. The tests always came back negative.