Noteworthy: Once a reserved show is published you cannot add or remove seats. If you do need to remove seats from a reserved show, you can place holds on the seats rendering them unpurchasable. If you need to add additional seats to a reserved show, you can only do so by adding in General Admission seats.
To change capacity on an existing General Admission show, go to the show's details page.
Click on the Set General Admission Capacity button.
Enter the new capacity number in the box and push save.
Your capacity is now updated!