Dexter told Delilah that the big chair in the family room is reserved for him. No one else is allowed to sit in this chair. The only exception is that Dad can sit with him if Dexter can sit on his lap and take a nap.
Dexter told Delilah that this chair is perfect for him because he can see the TV and the kitchen at the same time. Plus he can see the front door too in case someone comes to visit. He said he likes to know what is going on at all times and this chair lets him do that while napping.
He did also tell Delilah that if she is really good, he might let her try napping on this chair with him, but not not today.