Returns the number of measured criteria for an achievement.

Measured criteria for an achievement are shown in the default UI as details when clicking on an achievement in the achievements window or when showing an achievement in the objectives tracker; e.g. "Master of Arms" (15 criteria: Axes, Bows, Crossbows, Daggers, etc.) and "Safe Deposit" (1 criterion: number of bank slots purchased).

Not all achievements have criteria: achievements with zero criteria are those that can be completed in a single event (though a complicated event it may be), explained in achievement's description: e.g. "Reach level 80", "Fall 65 yards without dying", and "With all three Twilight Drakes still alive, engage and defeat Sartharion the Onyx Guardian on Normal Difficulty".