Ann: Demerger of The Lottery Corporation - Briefing Presentation, page-80

According to what I read, the fees need to be included in the original total amount...

"At the most basic level, the cost basis of an asset or security is the total amount invested in it, plus any commissions involved in the purchase."
Source: https://www.investopedia.com/ask/answers/05/costbasis.asp

Let's say I had 900 TAH shares before demerger, bough at an average price of $3.00 plus $19.95 in fees:

900 x $3.00 + $19.95 = $2719.95 per 900 shares, so it is:

$2719.95 / 900 = $3.022166667 OLD cost base per share

Given that:

"The Commissioner accepts that a reasonable apportionment is to attribute:
• 17.76% of the total of the cost bases of your Tabcorp shares just before thedemerger to the Tabcorp shares, and
• 82.24% of the total of the cost bases of your Tabcorp shares just before thedemerger to the corresponding TLC shares"

Source: https://hotcopper.com.au/threads/ann-ato-class-ruling-on-the-lottery-corporation-demerger.6806605/

Then:
2719.95 × 0.1776 / 900 = $0.536736778 is the new cost base per TAH share
and
2719.95 × 0.8224 / 900 = $2.485429867 is the cost base per TLC share


From previous posts, I think that is good.... But now...



Class ruling states that (Source: https://hotcopper.com.au/threads/ann-ato-class-ruling-on-the-lottery-corporation-demerger.6806605/):
"The reduction of share capital equated to $3.42 for each share in Tabcorp."

and also that:
"You will make a capital gain from CGT event G1 happening if the amount of the reduction of share capital for each Tabcorp share ($3.42) is more than the cost base of the Tabcorp share. If so, the capital gain is equal to the amount of the excess. No capital loss can be made from CGT event G1"

Given $3.42 is more than $0.536736778, there is a capital gain of the excess...

3.42 - 0.536736778 = $2.8833 <---- but how can this be?

Should the excess be instead calculated using the

3.42 - 3.022166667 = $0.397833333 <--- this makes more sense to me

Which one is right?

When and how do we choose the demerger roll-over? Does that happen when lodging the tax return?