Dec 2018 Q 3 a ii. Fill Co

(ii) how to calculate the net realisable value of the coal inventory, including the low quality coal
the answer provided states that :
Future changes in the forecast market price or the processing and sale of the low
carbon coal may result in adjustments to the NRV. As these adjustments are changes in estimates, IAS 8 Accounting Policies, Changes in Accounting Estimates and Errors will apply with the result that such gains and losses will be recognised in the statement of profit or loss in the period in which they arise.
Kindly explain why IAS 8 will apply here.
Thanks in Advance!!