former

While I am not quite sure which example you are referring to, I’d expect them to have sold/acquired assets for a difference in yeartoyear balance sheet accumulated depreciation and the reported depreciation expense in the P&L to show.
I’d say that the P&L reports the actual depreciation expense for the period, while the accumulated depreciation on the balance sheet may be affected by any changes of depreciatiable assets. To see if this hypothesis is true you would check if there is any change in the value of these assets.
Taking the difference on the accumulated depreciation and taking that value as the depreciation amount to be charged is almost certainly misleading in any real scenario.
Hope this helps. If you cite the page number of the example we might answer in more detail.