Returns the number of achievements completed by the comparison unit within a category.
Only accurate once the
INSPECT_ACHIEVEMENT_READY event has fired following a call to
SetAchievementComparisonUnit(). No longer accurate once
ClearAchievementComparisonUnit() is called.
See also Achievement functions.
id- The numeric ID of an achievement category (
numCompleted- Number of achievements completed by the comparison unit in the category (