If you are experiencing member attendances not being deducted from memberships, first check your method for event check-ins.
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The correct kiosk:

When using the kiosk, ensure that the class kiosk mode is being used rather than general kiosk. The general kiosk is intended for check-ins for the facility and will not count check-ins towards an event. The class kiosk which is intended for events will record attendance. 

Another area to check is your event settings. If the "Require active membership for members?" toggled off, this will not deduct an attendance from the membership. To check this setting, open the calendar, select the event in question, click "edit event" and toggle it on (green).