RetroCanuck

@mll source? this is taken from the NHL CBA

For the purposes of this Section 10.2(a), a Player aged 18 or 19 earns a year of professional experience by playing ten (10) or more NHL Games in a given NHL Season, and a Player aged 20 or older (or who turns 20 between September 16 and December 31 of the year in which he signs his first SPC) earns a year of professional experience by playing ten (10) or more Professional Games under an SPC in a given League Year.

Note that while the 18/19 age threshold refers to NHL games, the 20+ age threshold refers to Professional Games. “Professional Games” includes the following: any NHL Games played, all minor league regular season and playoff games and any other professional games played, including but not limited to, games played in any European league or any other league outside North America, by a Player pursuant to his SPC

I think this means his college year counted as a professional year.

College years don’t count as the player is not under NHL contract.  College is also not a pro league but an amateur league.

There are different definitions of pro season - for example towards free agency it’s 40 games to count as a pro season.  They look to be using the waiver definition of pro years.  Teves and Rafferty are eligible but Hughes is not.