You cannot change anything to revert back to the larger refund as you had not completed entering all your tax information. You need to enter all income slips for both spouse's and then look at the amount of the refund you are entitled to.

If you indicated that you were married, but did not enter your spouse's income, the program assumed that your spouse's income was zero, and applied the full credit to your return, resulting in the larger refund amount.

Entering an incorrect amount, or a zero amount, for spouse's net income might reduce the tax liability that the software calculates. However, the CRA will likely locate the error and reassess both your and your spouse's returns. In this case, you will be liable for the balance outstanding, as well as penalty and interest.

Why does the software show that my spouse and I I owe more money when we enter each others net income on our returns? Do married people pay more taxes than unmarried?

Your refund likely dropped due to the calculation of the Spouse or common-law partner amount.

Please see this TurboTax FAQ for more information: Why does my spouse's income lower my refund amount?