It's an order to engage BB and his crew. Means absolutely nothing in terms of Shiryu being stronger than him. Just because you're Head-Jailer asked to do your job by fending off an intruder doesn't mean you're stronger than said intruder.
He's the number 2 for a reason. Oda already hinted the number 2 color page wasn't about Vice Captains, it was about strength.
D: Hello, Odacchi! Looking at the cover page of Chapter 1031, it seems like Bepo is the No. 2 of the Heart Pirates, right!? I was surprised because I thought that Penguin, Shachi, and Bepo were all tied for No. 2! Are you saying that Bepo (with Sulong?) is the strongest between them? P.N. Pudding-ya
O: That cover, huh? Similar to Zoro, not all of those characters have the title of first mate. I selected the No. 2s as I saw fit. Usually, Shachi and Penguin are more dependable, but those two—who have seen Bepo's Sulong form—are no match for Bepo in terms of fighting power...! I acknowledge him.
That's as close to an explicit power level ranking as Oda is gonna give.
