Explaining the index expression of a random variable list

Question

This is my question, I have random variables with index i = 1, 2,...,k. I want to understand what this expression l = k - i, means in a simple form. I think l is the total number of the variables from 1,...,k. Can some assist me to interpret what l is from the expression above? Thanks in advance

Answer 1

Cleansing my crystal ball, I see the next:

l = k - i 

is number of items after i-th one.

 1   2   3     4   5  :   k
|__________| |______|
     i          l