When setting up or editing custom feeds the logic is to use 'or' within single filters and 'and' between different filters within the same feed.
In the example pictured we have a Feed that will collect leads that visit any of three different page titles as long as the Leads come from Belgium OR France.
The Leads/Companies don't have to fulfill each qualification, rather one in each group - Page Title and Country,
You can set filters to combine a number of different qualifiers in a flexible way, this is only one example to show how the 'and' - 'or' logic would apply.
It's good to keep in mind that also selected time period affects the results you see in a custom feed. If you have, for example, Page Title as a filter, the lead must have visited the selected URL during the selected time period to show up in the feed.
With these filters, you can create feeds that are highly focused or more open to showing you a list of the Leads/Companies that meet Your qualifications.
NOTE: If you use positive and negative filtering, for example, with the Tag filter, you get AND logic within the same filter. Otherwise parameters within the same filter type use OR logic.