Why does Tallahassee in ZombieLand say this?

When Tallahassee first sees Bill Murry, he says "6 left in the World one of them is Bill Murry!" Who's the 6th person????

1.) Tallahassee

2.) Columbus

3.) Witchita

4.) Little Rock

5.) Bill Murry

6.) ?????????????Why does Tallahassee in ZombieLand say this?
I always wondered about that too. He could know of someone else who's alive and is never mentioned...or (just thought of this) he could be referring to the girl Columbus' said he slept with in the back of a hostess truck or something like that?Why does Tallahassee in ZombieLand say this?
Aren't you a little obsessed with this movie if you are worried about it. Like most people, we was probably improvising and exaggerating.

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