If you have late seating dinner, your show will be at 6:30, before dinner.
Most cruise lines do the shows after dinner, no matter whether you have early or late seating.
One of the shows on our Eastern had a 2 pm matinee showing, plus the 2 evening presentations, and the Golden Mickeys had a third show at 10:30 pm for those who missed their "scheduled" show time, or those who wanted to see it again.
We always have late seating to avoid any rush for dinner or shows. With Disney, we did have a bit of a rush for the shows, but were glad we had the option of the 10:30 pm presentation of the Golden Mickeys.
I love Disney, but have cruised NCL RCL and HAL. Unlike those lines, Disney really is more of an "early to bed early to rise" line.
Having the late seating show before dinner adds to that.