When constructing a diminished seventh, the ‘seven’ is double-flatted. This continues the series of minor third intervals. So Cdim7 is C, Eb, Gb, A. The A is Bbb enharmonically. No, that’s not a typo. Thus there are only three diminished seventh chords before the pattern repeats.

Some years ago when we discussed all this, I believe that it makes a difference what style you are using, whether BIAB will play that double-flatted seventh.

If I recall correctly, either in Preferences Arrange or maybe Display Options, you get a chance to specify how you want this chord to look.
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BIAB 2022 Win Audiophile. Software: Studio One 5 Pro, Swam horns, Audition, Notion 7; Win 10 64 Pro. Hardware: custom i7 16 Gb; Roland Integra-7, Presonus Studio 192, Presonus Faderport 8, Royer 121, Adam Sub8 & A5X monitors