Gem copies limitation count towards spirit gems ?

You can no longer socket multiple copies of the same Skill Gem into your main skill sockets. Skills not granted by gems and skills socketed into Persistent Buff Skill Gems do not count towards this limit. does this LIMIT counts how many CoC i can have if yes that a big limitation towrds Cast On builds if yes please specify the SKill gems,Spirit gems bcs i already did my build and noticed it