Mr. R.’s World of Math

Zander entered the correct answer on the machine’s screen, and some words appeared on its outside.
“Look, it says, washing machine on it,” yelled Jackie.
“No, read carefully,” I said, “It says, wishing machine.”
“What’s a wishing machine?” asked Joe.
“I wish I knew,” said Matthew and then he kept talking, “Actually, I do know. A wishing machine is a machine that was sent by beings who live on a planet in another solar system. If someone squeezes the red orb on the top of the machine, a math riddle will appear on its screen. If the person figures out the math riddle, they will have whatever they wish for come true.”
“How did you know all of that?” asked Carlos.
“I don’t know, it just popped into my head when I said I wish I knew what a wishing machine was.” 
“Cool, we have a wishing machine!” yelled Jake.
“Yeah, all we have to do is figure out some math riddles,” said Regina.
“Can we try it Mr. R.?” asked Jenna.
“I guess we can see what it does,” I said as I wondered what a wishing machine really did do. “Who wants to try first?”
“I’ll try,” said Carlos as he raised his hand.
Carlos went to the machine and squeezed the red orb.
A math riddle for Carlos flashed onto the screen. 

If there are 6 of me, you have 4 less than 40? What number am I?

Carlos thought about it for a while, and finally he figured it out. What number did he have to type into the machine?