I'm seeing volume on 18/3/16 as 4283404.
On the ASIC short report there are reported total short positions of 4502253 on the 18/3/16.
If you look at the shorts on the 17/3/16 it was 3534945 total reported shorts.
The difference of 957,308 is the increase in shorts that occurred on the 18/3/16.