Fentress has the details:

As first reported by Baseball America and the St. Louis Post-Dispatch, Kelly has agreed to a contract that will pay him $1.6 million in signing bonuses, well over the $574,000 he was slotted to make as the 86th-overall pick.

That's a lot of dough. At a million over slot, I'm sure it was an easy decision for Carson. Here's wishing him the best of luck and hopefully we'll see him in a Cardinals uniform in a couple of years.