FXX / LLL Demerger, page-74

before they can distribute any of the assets of FFX to FFX shareholders they have to actually have those assets in existence (ie FFX will own all of the 200m/250m/500m/whatever LLL shares) - and then the Board of FFX will determine to distrubute 80% of those existing LLL shares as a capital return. How they get from the current number of LLL shares (you have a number) to the amount they need to undertake the pro-rata distribution will be via a share split/bonus issue.

So they will prior to the distribution already own their 20% that will be simply left in the central pot.