It's possible to specify a quantity available on a Package. If a quantity of 10 is specified, and 10 are sold, the item can no longer be purchased. The button for the Package on order forms says that it is "Out of Stock".

However, consider that you have 10 dedicated servers of the same kind. You sell 10, but 3 cancel. The Package is still not able to be purchased, even though there were 3 cancellations which freed up 3 servers. So, in this case it would be nice if we increment the quantity at the time of cancellation, so that the stock value doesn't have to be manually adjusted all the time.

This should be an option on the Package, because some items may not work this way and once they are gone they are gone, even if they are cancelled.

Add an option under Package Create/Edit next to Quantity Available, to the right of the input field where a quantity can be specified:

[ ] Restock

Add a tooltip that says:

If Restock is selected, cancelled services will add back to the available quantity.

Then, when a service is cancelled, and there is a quantity specified, and the restock box is checked, increment the quantity by 1.