I'm gonna guess that the negotiation would be whether Levi's ELC would kick in this year or next. I'm sure Buffalo would prefer to sign him to an AHL ATO for the remainder of the season and have the ELC start next season, but Levi might have some extra leverage now that they've dealt Erik Portillo.
Since Levi is a December 2001 birthday, he won't be considered 22* yet for ELC purposes and would have to sign a 3 year ELC if he turn pro now.
*Levi's college teammate Jayden Struble doesn't turn 22 until September 8, but would count as 22 if/when he signs and he'd get a 2 year ELC.