The “wort” is the actual gallon of liquid you will be fermenting with your starter. The wort will always be different depending on what kind of beverage you want to make.
The general recipe is for 1 gallon.
I was suggesting that you make about 4 cups of the ginger wort (boiling ginger in water for 20 minutes) and adding that to 8 cups your juice preference. That could be 8 cups of pureed strawberries or grape or peach juice. You do not have to do that though. You could simply use 12 cups of juice combines with your starter, lemon juice and agave. I would add some agave to help the wort ferment. It does not have to be a lot if your adding juice. Good luck and let me know how it’s going.