I posted a question weeks ago on why there is a digit printed on the packets of chilli and ketchup packets from McDonalds and Burger King.

Well, if you compare the colour of the tomoto sauce of a "2" verus a "8", you will see that the one with "8" actually looks much redder.

Therefore, the answer would be the concentration of tomoto/chilli in the sauce. Chilli sauce with a "7" would taste A BIT more spicy than the packet with a "3" printed on it.

Now that you know it, the next time when you order your food from the counter, you can tell them that you want the least hot chilli sauce ;)