Hi Bob,
The count doesn’t include automatic backups taken through the backup-before-plugin(/theme/core)-update mechanism (since if someone updates 10 plugins in a day, they don’t want to then find that 10 of their weekly backups got pruned). However, you’re right – it does include the ones created through hitting “Backup Now” too. So, the wording could be improved. I am not sure of a succinct description that can be used, and will need to think about it!
Best wishes,
David