How do I calculate California additional mortgage interest adjustment for home purchased in 2018?

[mrmrmr]

I had a 1 mil dollar loan for a home bought in 2018.  Since California does not conform to the new federal limit on deducting mortgage interest on loans over $750,00 and I am wondering how to calculate the "qualifying interest disallowed on federal state return"?

[Bees]

Do the regulations for the state allow all the interest you were charged during that year? Look at your federal return itemized deductions form for the amount already taken for federal and put in the difference between that and the total on your mortgage information statement.