I’m sorry to hear your designs are being printing off. The information you received from our other community members is correct.
Your Glowforge bed can accommodate materials measuring 18 x 20.4”. Your Glowforge has a maximum printable area of approximately 11″ (279 mm) deep and 19.5″ (495 mm) wide, and it’s reduced somewhat when the laser operates at high speed, as it can take space for the laser to decelerate.
This means not all of the bed is displayed, or available to be printed on, so there will always be about an inch of space on the left. This material can be reused as scrap later for small pieces. For example, a lot of customers use small pieces of scrap to print these pins available in the free laser design section: Honeycomb bed holdown pins
Let us know how it goes. We are here to help.