Depreciation calculation

One of the questions in Kaplan – “A Co has bldg costing 480000 with carrying amount of 384000 as of 1 jan 20×8. On that day it was revalued to 600000. The Co policy is depreciate bldg at2% st line basis and to make the annual transfer of excess depreciation”. Now, I calculated the initial depreciation rate and the new deprecation rate using the 2% basis. However, in the answer, it first uses the 2% and from there calculated the remaining years and then based on years calculated the new depreciation rate. So, I am confused. Why can’t we use the 2% rate in both cases? The new depreciation value is different if 2% is used vs using the number of years remaining. What am I missing here? Could someone pls explain? Thank you