Help with AMT and non-resident of Colorado return

Hello, I am hoping to get some assurance with a nonresident return for CO that I'm calculating a very large CO balance due.

The actual CO wages were only $1,871 but the total tax my software is calculating is $1,316 with CO normal tax being $79 and AMT of $1,237.

This person is a CA resident and their total taxable income per the IRS Form 6251 is $341,470 which is after Federal itemized deductions of $86,904.

When I look at the CO AMT worksheet, in additional to the CO income of $1,871, another $53,479 is being added which is from the CO DR 0104, line 4 – Itemized Federal Deduction Addback. I understand this to be $16k minus the amount on the 1040 line 12e (not including the state income tax, which is already being added back).

I guess CO is saying if you make more than $300k, you need to add your total itemized deductions to your income less $16,000.

Does this sound right?! I feel like I'm missing something. Trying to convince my client that on $1,871 of CO wages they're paying $1,237 in AMT is gonna be fun.

Thanks!