The AMT preference is based on the bargain element, which is based on the FMV on the latter of vesting or exercise date, minus the exercise price. The Form 3921 reports the value on the exercise date, without regard to the vesting date. TT calculates the bargain element from here as $12-$10, or $2 per share, when it should be $18-$10, or $8 per share.
