Hi,
Unfortunately there is no option to set this, as it also depends on the posts per page option on the WordPress back-end, which is statically set.
I usually recommend a custom code, if possible, but in this case there is no way around it, as the plugin is built to respect the posts-per page value set within WordPress core, and not to change it.
I will note this as a possilbe feature, and see if there is anything I can do about it to make it work on most cases.