Controls do not show all possible values

You can check the actual query sent to Elasticsearch in the Network tab of your web browser dev tools. Knowing which query is running and the response might give you an idea why the values are limited.

If all the expected values are returned from Elasticsearch but do not appear in the control values or the query sent to Elasticsearch is wrong then it may be a bug in Kibana. You can submit a bug report as a new issue on the Kibana GitHub repository.