Unit of measure denoting how many times the expression "ha" is to be repeated, indicating the speaker's amusement level.
Example -- Instead of saying,
"ha ha ha ha ha!"
the speaker may simply state,
"ha5!"
thus saving effort, and simplifying interpretation for the listener. This is especially helpful when the speaker is feeling quite jolly, and the number of "ha's" is very large, as in "ha50!" or "ha100!"