unknown subscribers

I activated the form on my site, so all good. The next day I notice I have 255 subscribers. Who are these mysterious subscribers? Are these some sort of default subscribers that come with the plugin?

There is no way I have 255 subscribers. I only had 70 visits in the time space anyway. They are under a list called ‘wordpress users’

can someone advise who these people are and if they ‘come with’ the plugin

thanks