make that something -- meaning?

A scene from the movie Pandorum (2009).

The Link to the audio file: http://tindeck.com/listen/guan (here's the YouTube version with a time mark set to take you right to when the scene begins)

Two guys wake up from hypersleep and find themselves on a spaceship floating in space. They don't remember anything from the past and must figure out what to do. One of them crawls into a vent shaft while the other guy communicates with him via something like an advanced version of a walkie-talkie. A few minutes further into the scene, that guy falls out of an overhead compartment, gets up, realizes that it was an overhead compartment he fell out of and says this, "make that an overhead compartment."

I asked an English native speaker and he said this, "he thinks he's in a locker on the floor but when he falls he realizes he was in an overhead compartment. Saying "make that a ____" is a common thing for jokes in movies like that. That's as much as I've got so far, but I'd like to know more about this turn of phrase.

Answer

"Make that a/an..." is a colloquial form of changing a former statement or request.

Your example:

I'm in a (place 1) -> Make that a (place 2)

This works even when statement 1 was made by another person:

Customer A, to waitress: "I'm having a beer"
Customer B, also to waitress: "Make that two."

(The underlying idea is that the waitress wrote down order no. one and now changes it.)

Later in the evening, you might overhear him adding a tip to the bill:

Waitress: "That'll be $16.

Customer: "Make that 20."