The data on a W-2 doesn't show a refund. Your refund or tax due is based on the total income on the tax return for the year, for both of you, and your total withholding, deductions, and credits. When you enter one W-2, your total standard deduction and any other deductions and credits are applied to the income from that first W-2. When you enter the second W-2, you don't get any additional deductions or credits. The full amount of income on the second W-2 is all additional taxable income. (You do get credit for the tax withheld on the second W-2.) So your total tax increases by the tax on the full amount of the second W-2.
