On January 1, 2023, Company A purchased a machine for $100,000 with an estimated useful life of 5 years and a residual value of $10,000. The company uses the straight-line depreciation method. On December 31, 2023, the company's management decided that the machine's useful life should be revised to 4 years, with the residual value remaining unchanged. Calculate the depreciation expense for the year 2023 before and after the revision, and explain the impact of the revision on the company's financial statements.