According to the guys replies to some follow up tweets it is a "translation of how their production in the ahl would translate to the nhl". He also says it doesn't take into account the lower quality of the AHL this year, but that "this type of production is so rare that its still very intriguing".
I just take the AHL stats and multiple by 2/3 for the first full NHL season. Over a few more seasons, a player should get to match of his AHL numbers in the NHL. After that, it is up to the player and team about how far he can go.
For example, Eeli Tolvanen played 58 and 63 games in Milwaukee and scored 15 and 21 goals. That averages out to 0.26 and 0.33 GPG or nearly 0.30 GPG. In the NHL, I would expect 0.20 GPG in his first NHL season. Eeli now has 11 G in 35 games or 0.31 GPG, so he is maintaining his scoring pace already!
Rocco Grimaldi averaged 0.40 GPG in his short stint in Milwaukee. He came with 37 games of NHL experience. This season, Rocco has 9 goals in 39 games for 0.23 GPG. During his 3 years in Nashville, he has scored 24 goals in 158 games for a 0.15 GPG average. His NHL totals are 29 G in 195 games for 0.15 GPG. His NHL scoring is
up 53% relative to his career.
Rocco is outscoring Duchene, who has 4 G in 29 games for a 0.14 GPG average season. Duchene's career numbers are 249 G in 822 games for 0.30 GPG. Duchene is at
46% of his career goal scoring average.
Rocco is scoring goals at 64% over Duchene's rate this season or Duchene is scoring at 61% of Grimaldi's rate.