Im not too sure about FF but 65535 seems to be the limit.
Maybe the game engine can use Factors. Such as 65535 as a Factor twice. or Powers?
But on looking, 65535 is 0xFFFF. Do they limit numbers above 65535 to be put in as Hex?
Sounds unlikely, but until such time as Square Soft ( I HATE Square Enix ) Releases source code, its unlikely we can really
make a large improvement on major game factors.
And the likeliness of Square Soft releasing source code, is as likely as Microsoft and IMB release OS/2 or Windows 3.1 Source code, Because it may be dead, but people could recreate Windows Vista with that sort of code.