My wife and I both live in RI. She works entirely in RI and I work in MA entirely. How do I do the apportionment of income in the non-resident return in MA?

The MA state return keeps asking me to apportion the amounts of income. And I try but it keeps coming up as an error when I check at the end of the return. They want spouse's Basis. But I can't change anything when it takes me back to it. It is question 13