Hi:

Follow the manufacturer's instructions for operating and loading the equipment. It might fit more jars but that space is for appropriate steam/air circulation to distribute temperature evenly over the containers and meet the thermal processing needed to make the product shelf stable. Overfilling it will cause a process deviation as the temperature will not circulate uniformly over the containers for the time required making them be under processed and allowing bacteria (particularly Clostridium botulinum - Botulism) survive = very dangerous. Stick to loading no more than eight pints at a time as per the manufacturer's instructions. Perhaps contacting the manufacturer directly can give more information. See if they have a mailing address/email or phone number.

Hope this helps. Thank you for using eXtension.