Do I need to convert 15 BBL into gallons? I’ve only ever used this to build my own recipes and I’m not familiar with any of the features really.

I got a recipe from a brewery and I want to scale it down to a 5 gallon batch. Is there an easy way to scale it down? I've been playing around with calculations in my head (and calculator) and it's taking forever and not sure if I'm being accurate or not. It's a recipe for a NEIPA and it's so...