From the Woolworths web site:
"The basis for cost base apportionment will be formally determined by the ATO and published by the ATO as part of the final demerger tax relief class ruling. The ATO is expected to publish the ruling in early August 2021.
Once the ruling is issued by the ATO, Woolworths Group will make an announcement via the ASX and provide further information on this website to assist Woolworths Group Shareholders to determine the respective cost bases of their Woolworths Group Shares and corresponding Endeavour Group Shares ."