Over the last twenty (one gallon) batches, I typically end up with 9 (12 oz) bottles. Along the way, there were a couple of 10s and a couple of 8s. With each batch, there was generally a couple of ounces 'left over' to taste test.
I have a 'one gallon' marker on the outside of my 5 qt bubbler and I top off to approximately that line when moving the wort from the kettle to the bubbler (I measured the marker using a one gallon water jug of water). I have a couple of ideas as to why I'm not getting 10 bottles (plus a taste test) every time - but at the moment, I'm happy when I get 9 bottles from a batch.