Is accelerated depreciation multiplied by the carrying value of an asset or its total value?

i.e. if we have an asset worth $25,000 with a useful life of 5 years and a salvage value of $5,000 using an accelerated rate of depreciation of 0% what is the assets NBV in every year?

From my understanding, depreciation expense would be:

Y1: 20,000 x 0.30 = $6,000

Y2: 14,000 x 0.30 = $4,200

Y3: 9,800 x 0.30 = $2, 940

and so on. However in one of the Schweser questions (in calculating the tax base), it calculates accelerated depreciation on the total value for each year i.e.

Y1: 20,000 x 0.30 = $6,000

Y2: 20,000 x 0.30 = $6,000

Y3: 20,000 x 0.30 = $6,000

This doesn’t make any sense to me… Can somebody please explain?