Overview
Audit includes files that have a limit that you can specify to control where your Audit runs. This might be used to sample 100 pages of many sub-sections of the site in a broad Audit. Or it could be used to access a few pages from several domains.
Each line of the include filter allows you to define the maximum number of pages to Audit for that filter.
Blank: This value cannot be left blank.
0: No maximum limit. The Audit will visit as many pages as it can after visiting the include filters with a number greater than 0. This is generally used to allow the Audit to visit pages after the other include filter limits have been reached.
Greater than 0: The scan will visit up to the number of a maximum number of pages defined here. The total number of maximum pages for all includes filters should not exceed the total number of pages in the Audit scan limit; a warning will display if it does.
Key takeaways
Include filters with a maximum greater than 0 are visited first.
Starting URLs are always scanned before any include filter URLs.
Include filters alone don't guarantee page visits; the system must discover matching links during scanning.
Conclusion
Setting the right maximum on an include filter comes down to what you're trying to control: use a number greater than 0 when you want a guaranteed sample from a specific section or domain, and leave it at 0 for a filter that should simply catch as many matching pages as the crawl finds.