You’re not specifying the number of posts you want back from the query, so it defaults to whatever you have set under Settings > Reading.
If you want all that match your criteria, then add 'posts_per_page' => -1 to your query arguments.
You’re not specifying the number of posts you want back from the query, so it defaults to whatever you have set under Settings > Reading.
If you want all that match your criteria, then add 'posts_per_page' => -1 to your query arguments.