General question about Calculated BUP offset for VTS

[slamjam0011]

Been recently backing up DVD to my computer and I notice on every few disk I get these three lines
Calculated BUP offset for VTS #1 does not match one in IFO header.
Calculated BUP offset for VTS #2 does not match one in IFO header.
Calculated BUP offset for VTS #3 does not match one in IFO header.
Although As far I can tell the backup seem fine due I need to worry about these errors?

[wmcclain]

I've seen those messages for years and they have caused no problems for me.

DVDs are not always authored with care and you sometimes see strange errors.