User blog comment:DoctorYes22/Question/@comment-35578328-20190420015542

They show if you expanded to page or made it smaller. If the numbers are green, the number is (I think) how many characters you added with that edit. If the numbers are red, it's how many characters you removed in the edit.

So if you edited a page and added more information that you removed, the green numbers will show how much you added overall.