itch.io

nvm

When gba ROMs are converted to .cia the ROM file is trimmed. The data in a .cia file might also be compressed, but I couldn't find any confirmation of that.

Gba ROMS always come in these sizes, matching the available configurations for cartridges:4-MB, 8-MB, 16-MB, 32-MB.

See:

https://gbatemp.net/threads/what-is-rom-trimming.365083/post-4977471

https://projectpokemon.org/home/forums/topic/22987-what-are-all-possible-rom-sizes-for-clean-dumps-gb-gbc-gba-nds/