Maxing out at 26 URLs submitted?

I have the plugin running on my multisite. I have ~40 sites going. the sitemap seems to be working but I noticed that each site map always has 26 urls in it... they are all different and related to each site but maxing out at 26...?

each of my sites has over 30 posts a day so is there a limit by design or bug that it maxes out at 26 urls?