Ohtani is deferring $68 Million of his $70 Million annual salary ($680 Million total) for ten years. He will draw the $680 Million deferred salary between 2034 and 2043. The advantages are two-fold: Reduced tax burden for Ohtani, and it keeps the Dodgers well below the MLB luxury tax threshold, permitting the Dodgers to more cost effectively pick up additional talent.
Ohtani earns roughly $45 Million annually in endorsements, in addition to his MLB salary. Nice gig for a talented young man.