I think it was 16 minutes each way. If he didn't leave Moselle until 9:22pm -- with a round trip of 32 minutes plus 21 mins at his mother's house -- he wouldn't be back to Moselle until 10:15pm. Unless my math is wrong. It does seem like he left Moselle at around 9:07pm.
I think he arrived at his Mom's at 9:22 and left at 9:43, getting back to Moselle at 10:00 (iirc).