Solved

33 cars in Elite league

What did you try to do?
https://igpmanager.com/app/p=league&id=1325&tab=info

What happened instead?
should only be 32 cars

Did the problem happen while using wi-fi, mobile data, or both?
Both

Did the bug happen in the app, on PC, or both?
PC

What operating system is your PC?
w

Which browser did you experience the problem in?
w

Can the bug be reproduced?
w

Additional comments:
w

This can happen if a manager joins a league prior to its final race but cannot partake due racing in another league in the last 24 hours.  This lack of participation in turn exempts them from demotion and allows more teams than normal to compete once premotees join from pro.

Exactly what Joshua said.
And don't worry, races will run as normal and next season this should fix itself (or earlier if someone would leave).