You got confused because you do not know exactly how many followers in your segment. Please follow our instruction:
1. You please go Contacts => Add Filter => Choose Segment
2. Select your segment and the number of followers will be shown.
Another case, you can know your number of followers by filtering more elements such as Campaign name, Status, etc,...
Hope this might be helpful for you.
Should you need further support, please feel free to contact us via live chat or email us at email@example.com