Ok I think I see now what's up, not really called bridging to me just moving the engagement zone up 10 feet . But if you have one skater within 10 feet(hips) of the pack in front, then 20 feet from her for out of play penalties. If she is pass 10 feet in front of the pack, then she is not part of the pack but still in play and there is no bridging here. So then the skater that was 10 feet in front of the bridging skater now becomes pass the 20 feet and can receive out of play penalties. Cool I think I am clear on this now and will remember to look for this on the next practice.
In rules 4.0 section 4.3 shows a diagram of the out of play, 6.5 explains the out of play penalties.