(any) Building's storage fraction, what iis it?

Probably asked and answered many times before, but I’ve not been able to see anything that confirmed what I’m looking at.
Let’s use the Blacksmith Forge as our example -
In Storage, I have:
5/60 iron
23/25 coal
Can someone explain to me what the fraction means? eg. on iron, is 60 the maximum capacity of iron this facility can hold?
I tried to math it up and say, oh, it’s a combination of the recipies and their needs, but nope, 15, 8, and 4 is not 60. It’s also not the makeup of how many workers are on any given task. So, what is it?


Hi, Your first deduction is correct, in your example: 5/60 means that it currently has 5 units stored and could have a maximum of 60.