Is there a video or a guide on controlling chord substitutions that I've missed?

It's mainly for the bass, it's flat out just playing the wrong note sometimes, I type C9 and it plays a low A sometimes and it sounds god awful.

How do I stop this? I know how to open the chord subs panel from chord settings but I have no idea what it all means without a some sort of guide.

It's rather frustrating...

Thanks in advance for any responses