Is the number of rss subscribers independent of the number of Google Followers? In other words if you had 50 google followers and 40 rss subscribers, then how many unique followers would you have? 90 or 50? I wasn't sure if there is an overlap.
They are separate follower counts, but there is no way to know if there is overlap. People might subscribe via RSS and not actually follow your blog with the "follow" link (and vice versa). I'd imagine that there is a lot of overlap, but you can't really tell for sure, short of polling people.