The 40/30/30 was the percentage of usage of the same square footage of the same Home 1 for each of three enterprises (C and two K-1's) I made up all of those numbers in your case probably two Office in Home (not homes), using Home 1 in each case and 50% for each.
Yes, there could be easier input, but I think it is not that common and this program has been in use for decades (Lacerte is under the hood of this model.) They just massage it as time goes on.