The “Must Not Arrive After” date is the last date on which you can enter Australia while holding this visa. You may enter Australia any time from the “Visa Grant Date” until the “Must Not Arrive After” date. If the “Travel Facility” is given as “Multiple”, you may enter and leave Australia as many times as you wish from the date of visa grant. The last date you can enter Australia is the “Must Not Arrive After” date. If the “Travel Facility” is “Single”, it means you can only enter Australia once.
Once you have entered Australia, you may stay no longer than the “Stay Period” given on your visa grant notice. This may be 3 or 6 or 12 months. The months are calendar months e.g. if you enter on 5 June 2017 and the stay period is 3 months, you must leave Australia by no later than midnight on 5 September 2017