The "Nightly Interval" essentially puts a maximum on the date ranges we search for.

For example, if you set your Nightly Interval to 3 nights.

We'll search for 1 night, 2 night, and 3 night stays in your calendar. 

If you have a large break in between bookings (ex. 20 days), we will break that into chunks of 3 nights so the data is more reliable.