No. You cannot claim a spouse as a dependent on your tax return. Each spouse gets a personal exemption on a married filing jointly tax return which is equal to a dependency exemption. If you are both under 65, your standard deduction would be $11,900 and each of you would get a $3800 personal exemption making the total $19,500. Did you enter your wife's name as your spouse in the Personal Info section and choose married filing jointly as your filing status?
Out of curiousity, I've been trying to figure out how it came up with 15,700. I can't come up to that figure. The only thing I notice is that 19,500-15,700 is 3,800 the amount of 1 exemption.