With the way pagination works in that API, it's possible to get fewer than the number of results you're asking for, even if there are more results in the total collection to return. You'll need to check if there are additional pages of results and crawl through all of them to build the complete set.

This is because of the way data is retrieved in the back end -- it includes archived data, data of other types -- all the filtering that happens for your result happens after the data is fetched, making additional API calls required to get the next window of data to be filtered and then presented to you.

Here's the relevant documentation:

It's possible to receive fewer results than your specified limit, even when there are additional results to retrieve. Avoid the temptation to check the size of results against the limit to conclude the results have been completely returned. Instead, check the next_cursor value in the response_metadata object to make sure that it's empty, null, or non-existent.