At the start of your run, you’ll see that the system gives you CR for free, which is why your first few games will give you 200+ CR, rather than the maximum 24 CR after placements.
From another thread, this is for RSS, but the concept is the same:
Fresh toon, getting +288 Rating for going 3-3, that’s the system giving them rating for free.
You may be good at your class, but you have no idea how the system itself works.