Precision to make it clear, the +12 db is automatically added to OT recordings, not to imported samples. After normalize, I’d definitely set AED Attributes GAIN to 0db for OT recordings.
With Master 0, LEVEL 127, VOL 0, you still have +12db headroom (with GAIN 0db).
VOL +63 adds +12db, so you reach (almost?) 0db with a normalized sample.
@danishdaycare did to check that :
Signal flow/gain staging diagram for Octatrack MKII