Got a bug with the big grids. Tried to race with 35 cars on Portimao. And with this feature it would be nice with a number of grid slots beside the track name. As well as the amount of liveries for each class in the class selection.
It is track related, try another track. And I think you need to make a change in your options as well.
This is actually a mistake It shouldn't be live just yet, and the way you have it is actually incomplete. (only menu allows it but there's nothing behind) It was removed for Spa and I think tomorrow it will be removed for the rest too. Spa will hold 100 cars in the combined layout