TL;DR for anyone wondering: This was made for inclusion into Factory Planner but never got added, it lets you create some rules (like "use only so many of this building") to basically spit out a full list of what you need to build to make, for example, 30 spm. Kind of like tools such as satisfactory planner, it intelligently derives a solution within your rules.
Thank you for making it available, i'm really looking forward to using it!!! Been looking at the PR every now and then for a few years haha..