Lets break it down:

K={24,26

Will return either {0,0},{0,1}, or {1,0}; meaning getKey≠24 or 26, getKey=26, or getKey=24 respectively.

Δlist(K={24,26

Will subtract the 1st term from the 2nd when there are 2 terms in the list it gets, and there are 2 terms in it. This difference is returned in a 1 term list.

So for getKey≠24 or 26 - {0,0}, 0-0={0}. For getKey=26 - {0,1}, 1-0={1}. For getKey=24 - {1,0}, 0-1={‾1}.

sum(Δlist(K={24,26

The sum of a 1 term list is the term in the list. Basically, it just takes the number out of the list and converts it into a real number, not a list. (Of course, this only works for 1 term lists.)

A+sum(Δlist(K={24,26

If getKey≠24 or 26, A+0. If getKey=26, A+1. If getKey=24, A+‾1 or A-1.

Magic, huh?

The next part is easy: max(0,A+sum(Δlist(K={24,26

The maximum of 0 and any positive number is that number. That's obvious, because all positive numbers are greater than 0. But 0 is greater than negative numbers. So if it becomes negative, the maximum of 0 and the number will be 0. That way it will never go under 0!

min(94,max(0,A+sum(Δlist(K={24,26

Use the same logic with min(). All numbers over 94 will turn into 94. The value of A will always be 0≤A≤94.

:min(94,max(0,A+sum(Δlist(K={24,26→A

Then store to A, the new value for A.

:min(62,max(0,B+sum(Δlist(K={34,25→B

It works the same way for B, just different getKey values and different max/minimums.