pascendi, the jurisdiction of the Church (binding and loosing) does not extend to the souls in purgatory: And whatsoever thou shalt bind upon earth, it shall be bound also in heaven: and whatsoever thou shalt loose on earth, it shall be loosed also in heaven. Catholic Encyclopedia ("Indulgences"):
To say that an indulgence of so many days or years is granted means that it cancels an amount of purgatorial punishment equivalent to that which would have been remitted, in the sight of God, by the performance of so many days or years of the ancient canonical penance. Here, evidently, the reckoning makes no claim to absolute exactness; it has only a relative value.God alone knows what penalty remains to be paid and what its precise amount is in severity and duration. Finally, some indulgences are granted in behalf of the living only, while others may be applied in behalf of the souls departed. It should be noted, however, that the application has not the same significance in both cases. The Church in granting an indulgence to the living exercises her jurisdiction; over the dead she has no jurisdiction and therefore makes the indulgence available for them by way of suffrage (per modum suffragii), i.e. she petitions God to accept these works of satisfaction and in consideration thereof to mitigate or shorten the sufferings of the souls in Purgatory.
"pascendi, the jurisdiction of the Church (binding and loosing) does not extend to the souls in purgatory..."
...to which you responded with the Scriptural passage which is at the bottom of this post, but addressing the same you also responded with this quote:
"...Here, evidently, the reckoning makes no claim to absolute exactness; it has only a relative value."
You're mixing two things:
1. Whether the pope can specify the exact number of souls released from purgatory, and
2. Whether the pope can declare that an indulgence can be applied to the holy souls in Purgatory, and more to the point, whether this is an action of "binding or loosing".
The latter is what the text I provided indicates. As to #1? I'm not sure. I can neither confirm nor deny that.
But your statement that the binding and loosing has nothing to do with Purgatory... to the contrary. It does include it, and the text I provide jives with that assumption.
The only disagreement here that I can tell is over this:
"And whatsoever thou shalt bind upon earth, it shall be bound also in heaven: and whatsoever thou shalt loose on earth, it shall be loosed also in heaven."
As to whether this includes those in Purgatory. I say it does; you may say otherwise.
It's a good question. I'm interested in it.