The Dink Network

I've been trying to understand how does that crazy 'Dink's Trunk' script works and I've got this question:

How can I isolate a variable number?

As some know, that script saves in a single variable every Dink's items with a monster number Ex.: 126532485

So, the third number from left to right is the number of bombs (maybe not, just an example) as we can see it's 4.

How can I take that number 4 out from that others and use it?

&trunk = 126532485;

&bomb = ???;