TAX – Chapter 24 – Example 2 ! Help please

Answer to Example 2
£243,200
The gift on 1 October 2008 to her son is a PET. This was not chargeable when made nor will it be chargeable on death as Dee survived for the required 7 years. The transfer is therefore exempt but will be deemed to have used the Annual Exemptions for 08/09 and 07/08
The gift on 1 June 2009 is a CLT and was chargeable when made but not on death as again Dee survived for 7 years.
The gift on 1 September 2015 is a PET and will be chargeable on death as Dee died within the next 7 years.
Step 1 Compute the Chargeable Transfers Transfer of value
Less: Exemptions
AE 09/10
AE 15/16
AE 14/15
Chargeable Transfer
AE 08/09 will have been applied to the 1 October 2008 PET despite it never becoming chargeable.
1/6/09 CLT 336,000
1/9/15 PET 296,000
(3,000)
(3,000)
£ Gross IHT Transfers
333,000 335,000 2,000
333,000
(3,000) 290,000
Step 2
1/6/2009 325,000 8,000
Lifetime Transfers Chargeable When Made CLT
@ nil @ 25%
= nil
= 2,000
As the donor, Dee, paid the IHT, the transfer is a net transfer and therefore the excess over the nil rate band is taxed at 25%
ACCA Taxation (TX-UK) (FA2019)
Answers to examples Paper TX-UK
Step 3 Lifetime Transfers Chargeable on Death
This is the hardest part of the question and requires us to firstly determine the earliest transfer within the 7 years before death as the starting point. In this example there is only one such transfer the PET on 1/9/15. However in computing any IHT payable on this transfer we must take account of what nil rate band is available after firstly deducting from it any CLT’s made within the 7 years of this transfer:
213
CLT 7 years < 1/9/2015 1/9/2015 PET No available nil rate band
= 290,000 @ 40%
Less: Taper Relief ((5-6 years) 60%)
= 116,000
Gross Transfers
335,000
290,000 116,000 625,000
(69,600) 46,400
IHT
Although the CLT of 1 June 2009 has drastically affected the tax payable on the PET of 1 September 2015 it will only be relevant for transfers within the following 7 years hence any transfer after that date (1 June 2016), or as here the Chargeable Estate, will not take account of this earlier CLT in computing any IHT payable.
The 7 year cumulation period at the date of death will only therefore consider the PET of 1 September 2015 in determining any available nil rate band.
As there is no mention in the question of a main residence being included in the estate at death there is no residence nil rate band to apply.
Step 4 Chargeable Estate at Death – 1 March 2021 Chargeable Estate
Available nil rate band = 325,000 – 290,000 = 35,000 IHT on Estate
35,000 @ nil = nil 465,000 @ 40% = 186,000 500,000

The above is the answer to Example 2 in Chapter 24.
Why is the 290,000 being deducted from 325,000 even though the NRB did not get used in September 2015?
Should not there be a full use of NRB in 2021 March (when he dies)?

Thank you