DSM has detected new login behavior (false positive?)

Does anyone know what triggers this warning? I've logged in remotely from many different locations and devices and just recently got this warning for the first time. This one was likely me based on the time stamp, location, and internet provider but I'm not 100% certain that it was. If this was me, why was I warned. If it wasn't, how does DSM know? Login was from my account, other accounts including default admin are disabled.