Low priority is a queue penalty, not your Behavior Score
These two get mixed up constantly, so it's worth separating them cleanly (see the table above). Low priority is a discrete, countable penalty: Dota drops you into a restricted queue and you exit by winning a set number of games. Behavior Score is the slow-moving 0–12,000 conduct number that decides whether you get sent there in the first place. The relationship is one-directional — a sinking Behavior Score triggers low priority, but clearing low priority doesn't repair the score. You can sit in low priority with a perfectly fine score after one bad-luck abandon streak, or carry a low score for weeks without ever being penalized.