This form of depreciation is used if you want to get a higher depreciation value at the beginning of the depreciation (as opposed to linear depreciation). The depreciation value is reduced with every depreciation period by the depreciation already deducted from the initial cost.
この償却法を使用すると、償却の初期に償却費が高くなります。償却価額は、償却期間ごとに、取得価格からすでに差し引かれた償却費の分減少します。