Forget this bet.

The issue is how to determine whether you are lying about winning a lot of money over a decade's time; that bet will neither prove nor disprove the claim, it will resolve nothing.

No, there is only one type of definitive proof.

that would be for you to show Dan your last ten years of tax returns, wherein I am certain (*ahem*) that you reported your gambling income as claimed.

Oh wait a minute, it would be child's play for someone to falsify copies of their tax returns.

Never mind.