Question wrt. revaluation and accumulated depreciation

Hi,
I’m studying for the diploma in Financial Mgmt and my BBP book has an example I don’t understand (see attachment)
Can anyone please explain to me where the accumulated depreciation of 400 k comes from ? I looked at answers from similar questions and everywhere it says that accumulated depreciation is reversed, the new value should be 5.6M and depreciation should be calculated from the new value and using the new estimate of the useful life…
Thanks so much for your help