Codebreaker.elf saying "Not enough space on memory card" after making edits (help!)

I'm trying to add Persona 4 codes on Codebreaker.elf for use on OPL, but whenever I make additions OR remove codes/titles, I get an error message saying: "Not enough space on memory card!" Help!

Edit: My mem card is almost empty. I should've said that before. Thanks @zfreeman