600 GB
I don’t think iCloud stores every bit. Doesn’t it store markers. Like why store same movie thousands of times for all users. Movie already in cloud, just store fact you have it downloaded to iPad. When restoring it would download from original source.
Now if you have unique drawings those would be uploaded to cloud. I have 200 GB iCloud account. Seems to be backing up my iPad Pro, iPad Air 2, and iPhone XS Max with room to spare. Think it’s only $1.99 a month if I remember right.
I agree if it's Apple content that it probably doesn't count towards your storage...it makes sense but I don't know if that's how it works or not.