Not the first time I've encountered this problem. We should accept the numbers spelled out too. In this case تسع or تسعة.
Here you can't use تسع on its own. You use it if there is a word after it.
when you speak of the number nine itself, you should use تسعة.
Selecting 8 is not a typo for 9! What is the point of asking if you accept any old answer?