Hi there and welcome
It means that someone from their smartphone or tablet tried to sign into your account and were blocked so it stopped them. They may have had access for about 1 hour.
This means they may have read your emails.
Do you have the IP address? and I can see where this came from as nearly always its someone you know.
because the login details where on the phone, so it was assumed you did this. You always need to reset the phone to remove all details.
Once you signed in from another location, then is it only possible to know the phone had unauthorized access.
With any smartphone, always factory reset it completely before giving it away.
If you would like any additional information or assistance, please do not hesitate to let me know.
Else if you can take a second to rate my service by clicking one of the stars at the top of the screen then submit, that would be greatly appreciated.