Hi Leah,
I'm not sure if there is an amount of time someone needs to be on a page... when testing I usually visit and close it immediately and I get counted.
If the lead is anonymous and visits >1 time they may show up as more than one number in the summary of your Visits progression status smart campaign. But they wouldn't show at all in the program, bc we have no info. If they are known, their status should only get changed once. It depends on your channel setup but generally a form fill (or CTA) has more weight than a visit. So If they visit, fill out a form, and visit again - they'd stay at the form fill status.
I'm not sure how you're campaigns are set but if you have anything else in the flow step (besides change program status), you set the flow when you schedule as to if you want the lead to run through once or multiple times.
I hope this helps!
Kim