Was it a single listing for multi items ? If so you only get 1 feedback count even if you sell 10 of them. You get 2 , 3 or whatever comments but only the single feedback count. It has happened to me several times. I had 30 pairs of disposable binoculars as a multi item listing I sold loads but only got a feedback count of one, but lots of good comments.
As I said a listing for multi items will only earn you 1 feedback point on your rating.
You may get 2 , 3 , 10 or more individual feedback comments from the buyers, but, you can only earn 1 feedback point from a listing even if the listing has 50 items available.