Yes, you are right, I missed out the first estimate. The...

Yes, you are right, I missed out the first estimate. The February one is actually the second estimate. I checked back and the November one you are referring to was detailed in Paul Thompson's presentation at the AGM in late 2016. I expect there will be a similar estimate given at the November 2017 AGM.
So in a normal crop year there are three estimates; November, February, and (April-May), followed by the actual crop figure released in late August.
We got an extra one this year once they discovered the blanks during the initial processing. Due to ASIC's continuous disclosure rules any event that has a significant negative or positive effect on the crop must be reported to the market.