Mr. R.’s World of Math

“We’re here,” said a worn down Joe, “finally!”
“I’m not going in that place! I’m at least 5/6 scared and 1/6 terrified!” yelled Jenna.
“Well, I’m 4/8 horrified, and 4/8 petrified!!!” added Joe.
“Finally you two agree on something,” said Jake, “I’m scared squared, but we have to go in to save Suzy Q.!”
“You’re right,” said Jenna as she banged on the big wooden door of the castle.
There was no answer, but the door slowly creaked open all by itself. The trio kept looking into the darkness behind the door, but couldn’t see anything.
Although they were terrified, they entered the castle. It was dark and they shined their flashlights into the big room they were in.
The first thing they saw was Suzy’s math notebook and one of her shoes lying on the floor in front of two large cages.
Inside the cages were what the students figured were Mr. Geebrah’s pets. The nametags on the cages said, Numer, the Dog, and Denomin, the cat. Numer the dog was in a cage on the top, and Denomin was in a cage on the bottom.

Speaking or Numer the dog, what’s the top number of a fraction called?