Shots on Goal Per 60 Min measures the average number of shots on goal a player has for every 60 min of time on ice, which is calculated by taking the total number of shots on goal a player has and dividing by the total number of time on ice and mutiplying by 60 (shots on goal/time on ice * 60).
More about Shots on Goal Per 60 Min
The basis for this statistic is that it equates for the amount of time on ice differences between one player and another that isn't reflected in per game measures - effectively, one is able to better compare the number of shots a player has on goal to any other player.