You fantasize about various things you could do, but you don't really think they could happen. Anyway, it is an interesitng thought experiment. If the program did work, what would be a good change to use to explore how the changes work? If you change someone else, you might not see all the effects in person. If you did some strange change to yourself, you might end up unable to change back. However, the change had to be big enough that you would definitely be aware of the change.
After some thought, it hit you. Age. You weren't "old," per se, but you were steadly approaching middle age. The late 30's were coming. You weren't actually self-conscoius about your age, but why not see if you can turn back the clock a few years? You don't actually want to make yourself have a later birthdate, but what if you could change the apparent age of your body? Create a scenario where you aged slower, so you still appear youthful? If it didn't work, no big loss, but if it did work...well, you could see the effects on the real world, and slow down your body's aging process at the same time, maybe buy yourself a few extra years alive. There's no downside.
But how far back should you go? You want to keep enough years to be independent - not an infant or too young a child - but enough for it to be a change that would affect all aspects of your life and people's memories of you. Although you scoffed inwardly at how serious you were taking this, you chose a number just before you pushed ENTER.