First, you might have overestimated the complexity of it. I tried to describe it as uncomplicated as possible without giving up the exact details of what it was, but I admit I might have failed at it. It was utterly trivial.
Basically we produced single packs and two-packs of a product and customers would order 1-n of them, sometimes with customizations.
The trivial but immensely tedious job was to make production and packing lists that took this into account.
I.e. with these orders:
Customer 1: 5 packs
Customer 2: 3 packs
That would end up like
Customer 1: 2x2-packs + 1 single pack
Customer 2: 1x2pack + 1 single pack modification x
Total:
5 2-packs
+ 1 single pack
+ 1 single pack modification x
Of course a real production run would have hundreds of these.
What I did once I got hold of the list was just to integer division (or what it is called) by 2 on each row to get the number of double packs in one column, something like (original number - 2x doublePacks) to get a 1 or 0 for single pack and then make a sum at the bottom for all columns.
I might have made som checksums too.
As for modifications I cannot remember anymore, I might have added some color or something, but once the immensely tedious first part was done it wasn't much of a problem IIRC.