Fluke 319 clam meter calibration - DCV offset

[LazyJack]

I have a Fluke 319 clamp meter (same as the 317 but with hiugher range, and I believe it is manufactured mostly for far eastern markets), which works just fine, but it has one Volt offset in DCV. Everything else is spot on. I'm guessing this is a calibration issue (no, you cannot zero in DCV mode with the Zero key).
I was looking for the calibration manual/procedure of this meter, but somehow I'm unable to find it. I don't want to just blindly press the calibration button, as most of the Fluke handheld meters I've seen won't work after that without doing a full cal. This is not a showstopper, I don't use this clamp meter for precise DC Volt measurement anyway and I can always add one Volt to the displayed value if I ever needed. Still, it would not bug my test equipmenet OCD if it was more accurate.
So, can anyone point me to the process, or know if is it possible to do DCV cal only?
Thanks.