I've not used that one, but I've used raspberry extract. In my case I use half the bottle in a 5-gallon batch and it gives just the right hint of raspberry flavoring without over-powering the beer. I think the bottle is 4 ounces. So if 2 ounces is good for 5 gallons, then in your case 0.8 ounces would be a good starting place for your maple extract in a 2 gallon batch.