Why was Tootsie Roll (TR) up 10% today?

$Tootsie Roll Industries(TR.US)$ I see it was moved from the S&P 400 mid cap index to the S&P 600 small cap index, which to me implies a downgrade. It seems counterintuitive to me that this would trigger a huge gain.

I’ve had a little of the stock for awhile, so I’m happy to see it go up, but I’m unsure how to digest this movement.