See my tips in red.
There are always exceptions to the case! From experience, many sellers will not be sure of exactly how many pieces instock they have, or more accurately, they won’t bother to check. Sometimes, an item is still listed for sale despite being out of stock, and the seller only informs after the item is paid for. So the indicated quantity on the page may not be the actual quantity available. For made-to-order items, it is even harder to gauge the exact amount of clothing that can be made. Usually, only small businesses and non-professional sellers would keep track of and update the actual stock availability of their items on their Taobao page.
Here’s a tip though. If the page states a large number for the stock availability (e.g. 9999), it usually means the shop has ample quantity of it or plans to restock it whenever necessary, but they may not actually carry that much quantity.
Are you seeing the phrase “此宝贝已下架” instead of the format above? That means that the item is unlisted from sale and cannot be purchased.