The numbers are well-defined, so you'll know them when you see them. Here's yesterday's so you have an idea what to look for:
![[Linked Image]](http://vometia.com/images/divinity/adventclue.jpg)
The numbers are typically blended into other things and have also been found amongst tree leaves, part of the decorations on pennants and so on. Once you've found a few you kind of train your eyes to spot them, though I'm suspecting the quizmasters may have some pent-up evilness to hit us with!
And just to be clear, so far it's always been a three-digit number, and always using a recognised font rather than "something that looks kinda sorta maybe".