Novelistic said:I sincerely think games with 0 achievements earned but time played should not effect our overall completion percentage.+1
This is the way Steam calculates total completion %, factoring out games that haven't had an achievement unlocked. I recall Xbox 360 games counting if you had playtime, but they could be deleted from your history until you had earned an achievement, so essentially the same behavior.
Steam is weird actually, each game is given equal weight, rather than reach achievement