Generally speaking, if you travel on one day, whether for 1 hour or 23, it counts as one day of travel, so if you are only travelling a short distance, it's worth considering just buying a point to point ticket if it's not too costly. However, you can hop on a train in city-number-one at 6 in the morning, jump off in place-of-your-choice at 10 for a look around, then get back on at 5 to continue your journey to city-number-two and that only counts as one day's travel. I'm not sure if you can go back to the original place or not - I haven't used a rail pass like that in a fair while. But I think there is a rule that if you get on board an overnight train or a late departure (check the Rail Europe link for details on this), you can put in the next day's date, and so you get travel the next day as well. Double check that, though, as I said, I haven't used a rail pass for a while.
Definitely not a dumb question - those rail passes are confusing as all get out.