When JSM is configured with Confluence Cloud as knowledge base, any related keyword search leads to only first 3 result showing up from space on all pages, regardless of how many items you get responded to as a part of search.

In other words, pagination does not work as quoted in Known Issues section.

It does not makes sense to have KB configured in Confluence Cloud and have only first 3 displayed as a result whatever page you navigate to while browsing the entire result.