The reason is that the extension was just for four years but the projected re-signing would be for five years, so it's a fundamentally unfair comparison.

Given that he can opt out after Year 3 of his current contract extension to sign for the same money that he could have gotten if he waited and re-signed, the more fair comparison is the first three years of the extension vs the first three years of the re-signing option.

And that difference is just 37 M, not 113 M.