I don't see a question but... the SFR of the softener is actually more important than the capacity, and both have to be taken into consideration to correctly size a softener.
The square foot size of the building has nothing to do with sizing water treatment equipment. Search for "softener sizing chart" and you can see how to correctly size your softener yourself. And you'll do much better price wise if you buy over the internet and install the softener yourself.
Quality Water Associates