Explaining Percentage Game Time and Percentage Match Time

What's the difference between these two metrics?

The most straight forward metric and the one people are most familiar with is Percentage Match Time (PMT) which is simply (expressed as a percentage):

Total Time on Field ➗ Total Match Time

Percentage Game Time (PGT) is a measure predominantly used in junior sport to evaluate a coach's / team's / club's ability to provide their players with a fair amount of game time. PGT is calculated as (expressed as a percentage):

Total Time on Field ➗ Total Available Time

Total available time is the amount of time that a player was able to play, discounting time lost to uncontrollable scenarios such as injury. The total available time is calculated as:

Total Match Time - (Time in Injury + Time in Assessment + Time in Disciplinary + Time in Absent)

To summarise with an example, a player might play the entire first half of the match but then pick up an injury at the halftime siren and not play for the rest of the game. In this scenario the player would have a PMT value of 50% but this same player would have a PGT value of 100% because they were on the field for the entire amount of time that they were fit and able to play.