How to stay busy?

So, I just recently changed careers from being a clerk cashier to being a data entry clerk for a much smaller business.
I typically work on entering timesheets and entering time into the payroll sheet so people can get paid and it’s a pretty nice gig apart from a few small problems here and there.
The biggest thing is that I usually finish everything bu about 12 or so. I’m trying to do things a bit slower to stretch it out but on fridays it’s especially tough to keep myself preoccupied and productive.
You guys got any advice for this?
I don’t want to make anyone think that I’m not taking this job seriously or I’m being lazy. It’s just the workload is in a weird limbo where if my manager were to do it, then she wouldn’t be able to do her regular duties but it’s not really enough to occupy a full 8 hour shift.