How do the built-in events use different signatures?

Looking at the built in event its only passing two method parameters: (It’s impossible to read but that says Erp.BO.POSvc, GetShipToAddressForSupplier)

If I try to do it the same way they are doing it, I get an error because I didn’t include the ds method parameter, which I also see in the rest help:

I don’t understand how they are using the method without passing the ds parameter?