Periodic Snapshot Tasks

I’m trying to understand Periodic Snapshot Tasks. The section labeled time start and time end… Does it take multiple snapshots during the time that’s selected? I don’t know what the difference between 15 minutes or 24 hours, what it does, what it means?

When it starts and if it is running too long, when to stop it.

Thanks for your reply.
How do I know how long to run it for? Why does it needs a time frame, instead of one specific time.
Example: I want a snapshot every other day at 6:00 am, How am I supposed to know if it needs to be 6:00 to 7:00? or 6:00 to 12:00?

Run a snapshot and see how long it take to do.