Someone's number is up the moment before they die. When used in the past tense, it means they were destined to die at the very time they actually did die. When used in the present tense, it might be a threat to kill someone immediately.
The phrase is perhaps based on the Take-a-Number System, in which customers take a numbered ticket rather than waiting in line. When the clerk calls out your number, "your number is up", and it is your turn to place your order with the clerk. Of course, the clerk might be the grim reaper instead!
Macafram: Yo man your name is always on Susies mouthpiece, what's the deal?
Nice N Scmoove: Yea don't sweat it, she's only fretting cause' my number one rule is run up through it released the fluid bounce out cause thats what im bout and she never knew it.
Macafram: Yo man your name is always on Susies mouthpiece, what's the deal?
Nice N Scmoove: Yea don't sweat it, she's only fretting cause' my number one rule is run up through it released the fluid bounce out cause thats what im bout and she never knew it.