Out-of-network multiplier
Discovery reach (For You beyond your followers) is a single multiplicative dial applied after everything else.
final = score × OonWeightFactor when the viewer doesn't follow you; special-cased for new users (account age < threshold AND following ≥ NEW_USER_MIN_FOLLOWING) and topic-pinned requests. All factor values withheld.
What it means for your posts
Everything that raises your base score raises OON reach proportionally; there is no separate 'viral switch' in the scorer.
See also the 22 scoring signals this adjustment is applied on top of, or run a draft through the checker.