How is the " State and Local Taxes greater than 10000 " Calculated ?

[StacyC]

There is a change from 2017 to 2018 for the amount you can deduct for state and local taxes (state withholding from your W-2, estimates paid to your state, property taxes, DMV fees, etc). For 2017 and before this limitation did not exist so you could deduct much more in state and local taxes, for 2018 either $10k or $5k is deductible, depending on your filing status. 

It sounds like your filing status for 2018 is something other than Married Filing Separately and the limit for taxpayers with your filing status is $10k. The worksheet is listing the full amount of these taxes that you entered, and then subtracting out the amount over $10,000 to get to your state and local tax deduction of $10,000. 

You can also visit this comprehensive article for more information about the changes from 2017 to 2018: 

https://ttlc.intuit.com/replies/6971774