What

Filters on the portal can be used to narrow down content to specific characteristics. Each filter can show up to 50 values

Why

This is by design. The portal filters are limited to 50 items and are sorted based on total number of results relevant to the search.
If for example, the filter displays only 50 organizations, but the University have more than that, the 50 organizations that appear on the filters are based on most related outputs relevant to the search filters with the orgs with most matches at the top.

More information

5.20.0 Release notes  
Note: Some of this information is for internal use only and might not be accessible.