没太理解为什么要减去3200 的revaluation surplus

问题如下：

A company has recently revalued one of its depreciable properties and estimates that its remaining useful life will be another 20 years. The applicable tax rate for all years is 30%, and the revaluation of the property is not recognized for tax purposes. Details related to this asset are provided in the following table:The deferred tax liability related to this asset (in millions) as at the end of 2014 is closest to:

选项：

A.£960. B.£690. C.£1,650.

解释：

Deferred tax liability = 0.30 × (£6,300 – £4,000) = £690

Only the portion of the difference between the tax base and the carrying amount that is not the result of the revaluation is recognized as giving rise to a deferred tax liability. The portion arising from the revaluation surplus is used to reduce the revaluation surplus in equity.

A is incorrect.It is the tax rate × writeup = 0.30 × 3,200 = 960.

C is incorrect. It is the tax rate × the difference between carrying value and tax base: 0.30 × (9,500 – 4,000) = 1,650.