I worded the topic starter volume question as opposed to starter amount question becuase I am wondering how the volume of the starter is accounted for in the total size of the batch. I have seen recipes for 5-gal high gravity beers that have called for as much as a 10 liter starter. You commonly see 2 and 4 liter starters recommended.
If you are brewing up a 5 gal batch, then add either a gallon or two more volume from the starter, you now have a 6 or 7 gallon batch. Of course the starter doesn't have the benefit of flavors from hops or specialty grains, so are you diluting the original wort ingredients by adding this starter? Are you supposed to compensate for that extra volume somehow? If you know you are putting in a gallon of starter do you calculate to come out of the boil with only 4 gal to end up with a 5 gal batch?