This tool allow you to modify every card stat in the game:

• Top, down, right, left value
• Elemental
• Power (When you lose a game card, the pnj will choose the card with the highest power value)

The card data is stored in the FF8_XX.exe file. Open it with the tool to load all the data, then modify the different values. When you save, it will create a .hext file with all the data modification to apply. It's a standard file understood by FFNx (or remaster).
The offset is computed for 2013 version. I didn't search (yet) the value on remaster, so even tho the data are fully compatible, the offset need to be changed.

Also, for the moment I only have 2 offset: English and French one. Choose the correct language when loading the file or when saving.

To use it, you need then to put your file to the hext folder. For example in FFNx it's in \FINAL FANTASY VIII\hext\ff8\en_nv if you play in english on the 2013 version.

Special thanks to @myst6re for finding the location of those data.