[Plugins: Jetpack] Non-email Followers

I am using Subscribe2 and Subscribe to Comments Reloaded for email subscribers. I installed both before I realized that Jetpack provided similar functions and I intend to keep them. After I installed Jetpack in order to get the statistics, it seems I enabled its subscription feature without knowing what I was doing. When I eventually realized that I had two subscription systems in place, I disabled subscriptions in Jetpack after manually moving the few subscribers there to Subscribe2. I was a little disappointed that the subscriber counts shown on the Jetpack statistics page did not disappear or go to zero but, since I believe the Jetpack emails have stopped, haven’t worried about it.

Yesterday I noticed the Blog subscriber count had increased by one. The new follower was not an email subscriber but a “regular” follower that has since vanished so I can’t give the exact name. So my questions are where did this follower come from (I see no “follow” button on my blog.) and what can I do to encourage and manage non-email followers? The site is:
https://www.dennygibson.com/blog/

Also, any information on really clearing the Jetpack email subscriptions would be appreciated.