Your UTC offset is how far your clock sits from Coordinated Universal Time right now. This page reports that, your zone's standard offset, whether daylight saving is currently applied, and the IANA identifier your browser uses — the four facts that between them describe your local time completely.
Offset, zone and DST are three different things
An offset is a number. A zone is a place with a history of rules. Daylight saving is one of those rules. Two places can share an offset in January and differ by an hour in July, which is why an offset alone can never identify a location — the point laboured, correctly, in what is my UTC offset.
Where the browser gets this
Your browser reads the operating system's zone setting and applies the bundled IANA rules. A VPN does not change it, because the zone is a device setting rather than a network property — explained in how browsers determine local time.