Paper size wrong

For whatever odd reason, Scrivener insists on formating the paper size as ‘other’ and a weird size.

I change it to US letter. Everything is fine. When I start scriv the next day, it’s right back to that weird size. Is there someplace I can force it to stay US Letter in Novel format?

ETA: this only happens in Scrivener. Pages and Word open/create 8.5 x 11 pages.