Recently, I am using WordPress Jet-pack plugin to connect my self hosting websites to Windowsphone app. And WordPress Json only shows 20 posts in my app post box. I wanted to display more than 20 posts. then I installed Json rest API, but it does not work or I did not change code to display more than 20 posts.
another solution that I applied is just attempt to change https://developer.wordpress.com/docs/api/console/ settings, but I did not change it. 
How to change WordPress API JSON post return limit?
I suggest to use WP API v2 plugin to deal with last version of WP API. Then you can use standart endpoint http:// your-domain.com/wp-json/wp/v2/posts and add filter ?filter[posts_per_page]=X, where X is required number of posts. Full endpoint will be http:// your-domain.com/wp-json/wp/v2/posts?filter[posts_per_page]=X. By default you will get 10