The Budgetary Process

I found this question in the revision kit (BPP Learning Media).

Budgeted sales of X for December are 18,000 units. At the end of the production process for X, 10% of production units are scrapped as defective. Opening inventories of X for December are budgeted to be 15,000 units and closing inventories will be 11,400. All inventories of finished goods must have successfully passed the quality control check. What is the production budget for X for December?

I worked out the answer and got 12960 units ([(18,000-3600)- 10% of 14400]) = 12960 units.
However the answer showed 16,000 units which had a working as follows:

Budgeted sales 18,000 units
Change in inventory (15,000units – 11,400units) (3,600)units
Required production units 14,400units
Scrapped units (10% of 14,400 = 1/9 of input) 1,600units
Production budget 16,000units

I am confused in the part where they calculate the scrapped units. As the question says, 10% of production units are scrapped as defective, which means what comes out as the production will have defective units which are 10% ( hoping that I am right). So my argument here is that, or question rather is that aren’t we supposed to reduce the 10% from the production units to get the production budget? I desperately need help with this concept.