What is the accounting issue in the following excerpt from the Wooden Toys Inc case?

Depreciation During December, when depreciation expense was being calculated, it was discovered that several manufacturing assets had been coded to the wrong general ledger account by the accounts payable clerk in the prior fiscal year. The assets had a total cost of $100,000 and, based on being coded as furniture and fixtures, were being depreciated straight-line over 10 years. WTI claims a full year of depreciation in the year of acquisition. After detecting the issue, management recorded depreciation expense of $30,000 on these assets in 2019 because manufacturing assets should be depreciated straight-line over five years at WTI. This means the cumulative depreciation is now $40,000, as required, and the assets are reported at net book value of $60,000. As changes in depreciation are treated as changes in accounting estimates, the change was made prospectively and there was no need to adjust the prior period financial statements.