ISO early exercised without 83 (b)

Hi, I didn't do it via TurboTax, asked a CPA to file the tax for me since I want to avoid any potential unknown mistakes. My CPA actually is not 100% sure for how to calculate the spread, but I read my company agreement regards the ISO grant, it did say that the spread for early exercise ISO will be the difference of FMV at the time of ISO vesting and your strike price, not the FMV at the time to do the early exercise, assuming my company lawyer is right.