Most API calls accessing a list of resources (e.g., users, issues, etc.) support pagination. If you're making requests and receiving an incomplete set of results, you're probably only seeing the first page. You'll need to request the remaining pages in order to get more results.
It's important to not try and guess the format of the pagination URL. Not every API call uses the same structure. Instead, extract the pagination information from the Link Header, which is sent with every request.