Is there a formula used for the initial power rating of a team?

USCL specifies that the rating is based on the sum of the average goal differential and average power rating of competition. Part of your rating is based on the rating of your competition. But at the start of all of this, there is no rating for your competition. So how do they calculate it. You can't just say "based on last year" because the same thing applied last year. Does someone make up a rating score at some point or is there an initial formula?

I actually like the system (but I'm unsure if any system should be used for 6th graders). I think it's pretty accurate, just don't know how the initial ratings are determined.