Yer, sadly its more complex than that.
A bit of history,
BF2 had a max bot count of 32 till 1.5 patch
That patch raised it to 48 and the toggle allows this.
However, FH2 never changed its aidefault.con file (This is fixed now) so we still had a fix of 32 bots, even though the toggle said differently, that made it such that any adjustment you made, dumped the remainder on one side.
Now once you change the bot count to 47 in the aidefaults.con file, you get everything working well.
If you want more bots, you simply need to realize that since 48 bots allowed 50:50 ratio ingame, and 48 is almost 50, then 64 bots needs to be adjusted to a ratio of aprox 64 to restore balance.
So at max, you can have 100 bots at 50:50 ratio when you push the slider to 100% ratio.
Once you set that slider and adjust the bot count in the file, the biasing of bots to one side is up to you. Just rememer where the 50:50 position is for the number of bots you set.