What is obi?
An obi is the paper band around a Japanese book. In Hondana the same word is the short label for a collected format, such as 3-in-1 or 2-in-1, shown on a shelf entry.
The paper obi is a publishing object: a promotional strip, often removed and sometimes collected on its own. Hondana does not inventory paper bands. The badge you see in the app is a reading aid. It says, at a glance, that this entry covers more than one story volume.
The badge is derived from the volume range and the edition's format. It is not a separate fact you have to maintain. Change the range and the label follows. A true single has no obi badge.
If you are searching for the paper band itself, this is not that record. The useful question for a shelf is which physical book you have, and the range answers it.
Related
See the words on a real set in the edition catalog.