There is a literal panel saying SEVERAL, not 1, not 2, SEVERAL,
TENS
of minutes.
I say 20-30 minutes because that is what that panel is specificially saying.
Oda being inconsistent with other events is irrelevant, this was clear mapping the duration of Luffys 1vs1 against Kaidou with an event that happened on the roof, 30 minutes is the upper bound it cannot be greater than and 20 minutes is the lower bound that it must be more than.