For this application, it shouldnt really go under the mid 11s ideally as it starts to drink fuel if you do and there is no real need to run that rich.

On some cars with badly designed exhaust manifolds though you do need to be down that low just to control the temps.





The reason its a higher number for leaner, is that the ratio is part of AIR per part of FUEL.
So the less fuel in the ratio, the more parts of air per part of fuel.

Dont be surprised if you see 16s etc for a split second here or there when going on and off the throttle etc, its not an exact science on these cars so dont expect massively consitant results on every possible condition,they're a bit basic for that no matter who is mapping them!