Chattel acquired for >£6,000 sold for <£6,000

fairf

I have been doing exercises on capital gains tax (based on FA2012) in the green light area of the AAT website.

With regard to selling a chattel for <£6,000 when it was acquired for >£6,000, I understand that the deemed proceeds become £6,000 and then the cost of the chattel is subtracted. However, can you then subtract selling expenses to increase the loss?

In one green light question it appeared you could.
ie deemed proceeds £6,000 - selling expenses (auction commission) £750 - cost £7,500 = loss £2,250
[man sold a piece of furniture at auction for £5,000 on which he incurred 15% auction commission]
[so gross actual proceeds = £5,000
and auction commission = £5,000 x 15% = £750]

However, in another it appeared you could not!
ie deemed proceeds £6,000 - cost £7,000 = loss £1,000
auction commission of £500 ignored
[painting sold at auction for £4,500 at auction after 10% auction commission]
[so gross actual proceeds = £4,500 X 100/90 = £5,000
and auction commission = £5,000 x 10% = £500]

I am confused. Could anyone help, please?

fairf