Exactly that
The first number is the pod packs primary design, it has 4 ‘tubes’ to securely hold 4 pods
The second number is some extra elastic slots, it can take an extra 7 when you need to
The extra elastic isn’t as secure - which doesn’t mean they will fall out but they can be wobbly. You don’t want to be running a lot with a full pack, and it is harder to put your empty pods back in to the elastic. That’s fine on a tournament field but in the woods you could be leaving pods behind or dropping them into your jersey