Common mathematical prose has no concept of assignment. Instead of "assigning" something to a variable, you just define things by explaining enough of their properties to make it clear which thing you're describing
Now let $\mathit{Correction}$ be the function [or vector or whatever] defined by
$$ \mathit{Correction}(i) = \mathit{Bin}(i) + \mathit{offset} \qquad \text{for all relevant }i $$
...
This is a perfectly good definition -- the only requirement is that the reader can convince himself that there is one and only one thing that satisfies the condition you're giving.
(Of course, depending on the notation you otherwise use to represent the things in your code, you might want to write $\mathit{Correction}_{\,i} = \mathit{Bin}_{\,i} + \mathit{offset}$ instead. That doesn't change the general principle).