WIP Quindell PSD acquisition

Can someone help me out and explain how Quindell PSD acquisition's WIP was determined by Slater?

The WIP was stated as 420mil AUD in the link below:

http://www.asx.com.au/asx/statistics/displayAnnouncement.do?display=pdf&idsId=01614864

No where in the announcement did number get explained. Did they just use Quindell's inflated annual report at the time to estimate that figure? As we know, subsequently, Quindell was found to have overstated that number by up to 10 times of what it should be by conservative accounting.

Mr. Grech has affirmed in the below link that his own lawyers did the estimation case by case. But how come his estimation is closer to the original Quindell's overstated amount and far from the UK investigation result?

http://www.asx.com.au/asx/statistics/displayAnnouncement.do?display=pdf&idsId=01636010

For those who can help me out, please use primary sources and links with your answer. Thank you.