Exam preparation question – Non- current assets under Chaper 7. Impairments

Dear tutor,
I am struggling with this question as the answer to equity amount is different from what I understand.

(b) Adjustments to retained earnings $’000
Draft retained earnings 7,350
Profit on disposal
(=$2,500,000 – ($4,000,000 – $2,000,000)) 500
Depreciation – factories -3,260
Depreciation – office building -625
Impairment -2,875
Depreciation – office building -700
390

The depreciation charge on the revalued asset will be different to the depreciation that would have been charged based on the historical cost of the asset. As a result of this, IAS 16 permits a transfer to be made of an amount equal to ‘the excess depreciation’ from the revaluation surplus to retained earnings.
But the above workings just transferred all the depreciations charged for both building and factories.

How may I understand the workings that concluded in $390 of equity value?