Ann: Director Appointment/Resignation, page-12

Here the calc in the demerger booklet.

Under the Demerger, the Capital Reduction Amount
will be calculated using the following formula:
A = (B / (B+C)) x D
where:
A = Capital Reduction Amount;
B = Webjet B2C market value, being the VWAP of
Webjet B2C Shares for the first five trading days
starting from the date of the commencement of
trading (including on a conditional and deferred
settlement basis) of Webjet B2C Shares on the
ASX multiplied by the number of Webjet B2C
Shares transferred to Shareholders (or the Sale
Agent) under the Demerger (which will equal
the number of Webjet Shares on issue on the
Demerger Record Date);
C = Webjet market value, being the VWAP of
Webjet Shares for the first five trading days
starting from the date of the commencement of
trading (including on a conditional and deferred
settlement basis) of Webjet B2C Shares on the
ASX multiplied by the number of Webjet Shares
on issue on the Demerger Record Date; and
D = Webjet Share Capital Amount.