Indicates for how many successive days you can live on pasta (plain or with something) without turning grumpy. Especially important when you are a poor student. If you are beyond your pasta tolerance treshold (PTT) you might want to switch to rice, polenta, potatoes etc. for a few days until you reach, for example, your rice tolerance treshold (RTT).
"Ey dude, pasta
for dinner tonight?"
"No man, I'm really beyond my Pasta Tolerance Treshold. I'm going for rice instead."
"Alright, I see what you mean. Your PTT is not to be messed with!"