PP, sorry, but it will be 8,000 each way; a total of 16,000. That's still less than 20,000 however.
You need to see the
definition of a "trip" from the Qantas Frequent Flyer terms & Conditions.
Originally Posted by Award Flight Changes
The number of points needed for an Award flight on Qantas and our Partner airlines will be calculated on the sum of the one-way trips+ in your itinerary. There will be no charge for stopovers, or for any non-flown (surface) segments.
'+Trip' means:'
(i) a series of consecutive Flight Segments not broken by a Surface Segment, Stopover or Turnaround Point;...