Supposedly, they are logging in office time via your computer connected to the network. VPN or not, your sourece IP address while in office will always be a 10.x.x.x. VPN IP will be different.
They are looking for at minimum 1 hour in office - which I assume is to prevent "coffee badging."
I don't know this 100% for sure but this is what Ive heard lately so, for those of you RTO id spend at least an hour in office...