2015 CA STATE TAX NOTICE OF PROPOSED ASSESSMENT

I recently received a letter from the CA Franchise Tax Board regarding my 2015 taxes.

 

They are proposing additional tax in the amount of $532.14. Reason given is "You did not provide substantiation for the itemized deduction adjustments claimed on your Schedule CA (540)-California Adjustments- Residents.

 

Any idea what this could mean? Everything always transfers from my Fed to my State. No errors on the return.

 

Any idea what this means?