In Avatar (2009), a man speaks to a pilot in a jet via radio:

MAN :Valkyrie 1-6, copy...Valkyrie 1-6, you are clear for de-orbit burn at 2-2-4-niner.

Pilot: Copy, Venture Star. Go for de-orbit burn at 2-2-4-niner.

What does "2-2-4-niner" mean?