Having trouble keeping my “activity” high

I believe I have what people call a “cushy” job, it is not stressful, I don’t really talk to anyone besides my manager and a mandatory weekly meeting. Extremely flexible hours and almost no micromanaging.

I intend on keeping this job for a long time, the pay could be better but I think the other perks cover that. My company uses a tracking tool to check how many hours you worked and your pay at the end of the month, this tool takes screenshots and also tracks mouse and trackpad activity.

My “activity” has always been on the lower end, and I just don’t know how to make it go up. I’ve never missed a deadline, I’m actually ahead in all my work, I consider myself a reliable employee (my manager agrees with me). I don’t go out of my way like crazy trying to re invent the wheel but I’m always trying to do better.

I was called out about this once by my manager in a 1-1 where he mentioned some gaps in the workday (moments where there was 0 activity) and I told him it had been a period of rather slow things at work (there are other periods where we get busier which I think it’s perfectly normal, right?)

Anyways, he never mentioned that again and it’s been months. Even in crazy busy times my activity goes up by 3-5 points in a scale from 0-100. However, I’m worried that I might be taking this job for granted.

I always assumed it was better to not mention anything but I don’t know what to do now, should I bring this up? How can I make my activity levels higher? Thinking about this because yes it’s been slow and honestly I don’t know what else to do.