If it works similar to the layout priority for tracks, the larger the numbers in the priority field, will more be prioritized. For track layouts it means shown "first" when the track is selected. For skins, I think it will mean skins with larger numbers (not sure if you have to keep it limited to the total number of skins you have for the car), will be picked above skins with lower priority when it comes to assigning AI skins for cars. I think also, you can share priority numbers (if you have more than 1 skin you want to be prioritized when CM applies skins to AI)
Hopefully someone who knows for sure can correct me if I'm wrong
Since about a year ago and a few CM / csp updates, shadows for a lot of my cars are wonky. If the issue is just in the showroom, and not on track, usually "update ambient shadows" fixes the problem.
You can do it car by car in the CM Showroom (after first click, then click update again)
View attachment 1366518
Or as I learned recently, batch mode when selecting multiple cars
View attachment 1366517
Some cars (mainly new URD mods) don't seem to have a shadow and this option doesn't work. Only the CSP preview showroom option can create a shadow for them and only in their preview, not CM showroom view.