In 8a14 they are using the process account to find the missing figure (the value of the input), and in the process account we always put the abnormal loss at full cost of production.
In 8a17 they are asking for the amount to the statement of profit or loss in respect of the abnormal gain, and the gain in the profit and loss is the fill cost of the abnormal gain less the scrap proceeds that they are not receiving.
I explain all of this in my free lectures on process costing.