T2203 and T1139

I have a client whose situation is probably unusual. The client resides in Alberta but is proprietor of a small business located in Ontario. The business has a non-calendar year-end, so business income from T2125 has to be adjusted on T1139 and the client’s income has to be allocated between AB and ON on T2203. I understand all that (I’ve been been doing tax returns since 1967).

What I don’t understand is why TaxCycle’s T2203, column 2, picks up the net income from T2125 line 9946 rather than from T1139, Part 4, line G. I can override, but why should I have to?