New to WFH with a light workload but tracking required

I’m new at my job and work from home 3 days a week. My workload is still light since I just started, so some days I genuinely run out of real work. I’m on salary, and required to log 8 hours of tasks per day (no specific time-tracking, just task logs).

Looking for advice on two things:

Logging honestly: how do you fill task logs without it looking like you’re doing nothing, when there just isn’t 8 hours of work yet?

Actually filling the time: if you’ve been in a similar situation, what do you do to stay occupied/sane? Courses, side projects, personal admin, anything that feels productive but doesn’t blur into “not working”?

Thanks everyone!!