[Koha] Opac display

I'm new to Koha and I would be grateful for some help. The name in the "Label for opac" in the MARC framework does not correspond to the actual label on the opac. For example: In the Admin module one of our frameworks has the following labels for 246: "Label for Lib" = Variant title ; "Label for Opac" = Variant title. But in the Opac display the label in fact reads: "Other title". In which part of the Admin module do I tweak with these labels? Why the discrepancy? Is there any video online where this topic is covered? (I could not find any). Many thanks for your help. Carlo