From Garry's Mod
Retrieves progress of given achievement
The ID of achievement to retrieve progress of. Note: IDs start from 0, not 1.
Will print achievement progress for all of your achievements into console
for i = 0, achievements.Count() - 1 do print( achievements.GetCount( i ) ) end
Prints achievement progress for all of your achievements into console. Note: Non-progress based achievements will have 0, even if they are completed