Major capital improvement, new cost base and CGT calculation?

Hi CGT experts,

Have been reading this link https://www.ato.gov.au/Forms/Guide-to-capital-gains-tax-2013-14/?page=92#Major_capital_improvements_to_a_dwelling_acquired_before_20__160_September_1985
few times over and it’s doing my head in trying to understand it but to no avail.

To put things in simple terms and perspective, got a resi IP bought in 2001 at $410K, subdivided it
couple years ago and still retaining both lots so that was no CGT event.

Now, I plan to sell off one block with the rented property on it but like to do some reno to it before
sale to try getting a good price for it. This leads me to research CGT treatment related to major
capital improvement and also what extent of reno works is considered a legit major capital improvement
in order to work out the correct cost base and resulting CGT.

Anyone has similar prior experience able to share to crystalise it much more clearly than the example
on the above ATO link?

Thanks,
FXD