How is the number of logins retrieved?

Hi,
recently I installed this plugin and was happy, because it’s not bloated like other plugins.
But since then I get a lot of complaints from users, who can not login anymore and I see their attempts to get a new password.
I installed another plugin, that shows the currently logged in users and remarked, that the number of logins for myself grew, although I didn’t change anything.
So I wonder, how this plugin counts/retrieves the number of active logins. I can’t tell for my customers, but for myself I know for sure, that I am only logged in once and not (now) three times from the same IP address.
Beste regards