Cost of inventories sold

I have a question concerning the cost of inventory which I hope someone can kindly help me resolve.

In the text manual, the cost of inventory recogised as expenses is shown as follows:
$
Cost of opening inventory 140,000
Purchase 670,000
Cost of closing inventory (155,000)
Opening NRV provision 30,800
Closing NRV provison 55,500
(Increase/decrease in NRV provision (24,700)
__________
Amt of inventories recognsied as exp 630,300

The closing stock, after making allowances for the impairment, was $99,500 at the yaer end date.

I am really at a loss as to how to work out $630,300 as the cost of inventories recognised as expenses becaue to me , it should be $679,200, calculated as opening stock ( 140,000 – 30800( impairment provison)PLUS purchase ( 670,000)LESS closing stock (155,000-55,500( closing impairment provison).

Could someone kindly give me help as to how to work out the cost of inventories as HK$630,300 and what are the double entries required?

I look forward to receiving your kind assistance.