To use the quantity field in a bill you need to use a product/service item. So to do what you THINK you want to do (which I will later explain is just plain crazy) you need to add a "product" that posts to Fixed Asset>Office Furniture. Then you would be able to post the Bill for 9 chairs.
BUT WHY??? The Safe Harbor de minimus rules allow you to directly expense office and other equipment which cost you less (including tax and shipping) of $2500 per line item. Unless these are $3000 chairs why go through the frustration of adding these 9 chairs to your depreciation schedule and instead simply write them off same as you would with your printers, tablets, PCs, lawnmowers, chainsaws, weedeaters, refrigerators-stoves and other appliances, etc.
