This trope can take a variety of forms, but always involves one character stating some quantity in the form of a number, and being quickly corrected by another.
It can be used to establish backstory.
It can be used to establish some amount as fantastic or unthinkable.
- The Lord of the Rings
Grima: "Even if [Helm's Deep] is breached, it will take a number beyond reckoning, thousands, to storm the keep."
Saruman: "Tens of thousands."
It can be used for comedic effect.
There are more examples, but this is just to give you the basic idea.
- Transformers pilot
Spike: "Wheeljack wasn't kidding when he said it would blow up in 60 seconds!"
Wheeljack: "59.99 to be exact..."
- Star Trek (2009)
Kirk: "What would you say the odds are on our gettting out of here?"
Spock: "It is difficult to be precise, Captain. I should say approximately 7824.7 to one."
Kirk: "Difficult to be precise? 7824 to one?"
Spock: [Correcting him] "7824.7 to one."
Kirk: "That's a pretty close approximation."
Spock: "I endeavour to be accurate."
Kirk: "You do quite well."
- It's A Terrible Life
Ed Zeddemore: "You have to burn the remains. Okay, this next part gets a little gross. Sometimes you might have to dig up the body. Sorry."
Harry Spengler: "It's illegal in some states."
Ed Zeddemore: "All states."
Harry Spengler: "Possibly all states!"
- Uptown Girls
Ray: "You're late."
Molly: "By like a second!"
Ray: "Three and a half minutes."
- The Social Network
Delpy: "The site got twenty-two hundred hits within two hours?"
Delpy: "I'm sorry?"
Zuckerberg: "Twenty-two thousand."
Delpy: [to herself] "Wow."