You are correct that a total of 4 exemptions on a tax return
would total $16,200. However, there is a
phase-out range that reduces the exemption amount depending on the Adjusted
Gross Income (AGI) and filing status.
For a 2017 Married Filing Joint return, the phase-out begins
when the AGI exceeds $313,800.
To read more, use the following link and see page 23 of the IRS
Publication 501: https://www.irs.gov/pub/irs-pdf/p501.pdf
Also take a look at the information below.
https://ttlc.intuit.com/replies/3299967
