Cgt:Relief for individual

Q- On 30 September 2022, Eleni made a gift of a house to her grandson.

Kostas. The house had been bought by Eleni on 1 September 2009 for £45,000 and was extended at a cost of £10,600 during June 2010. A market value of £140,000 at 30 September 2022 had been agreed by HMRC. Eleni occupied the house as her main residence until 30 September 2018, a period of 109 months. During this period, Eleni rented out one

third of the house for 96 months. The tenant did not share any living

space with Eleni.

Eleni then went to live with her sister for the remaining 48 months, until

30 September 2022.

Calculate the chargeable gain after reliefs arising on the gift.
—————x—————x——————-x——————-x————–

Doubt –

To calculate prr…
Total occupancy is – 157
Lived in full house total(m) 13 exempt 13. And chargeable ——-
Lived with teanet. 96. 64. 32
Lived with sister. 9. 9
——— 39. — 39

I’m confused why the last 39month is chargeable when in the book it is written that person can be absence for 36month for no any reason. So chargeable month should be 39-36 = 3..
Please correct me if I am understanding the concept wrongly