Custom cube randomized when opened?

I've tried to open up one of the cubes on here using Forge, but whenever I do, it just shows a random card pool. I've tried looking on here, but to no avail. Is there anything I could do to fix this?
High Quality Resources for Collectible Card Games
https://www.slightlymagic.net/forum/
https://www.slightlymagic.net/forum/viewtopic.php?f=26&t=14245