Assuming that what you are trying to do is point your root domain (brainiate.acedmy) to brainiate-academy.teachable.com you already have 8 records for brainiate.academy. You would need to delete the 4 A records and 4 AAAA records for that same host name which already exist to instead point to teachable.com.
Right, before you were trying to add the root domain, not the www. You should now be able to add the root domain (you can use an @ to represent that for the name).