Elan 7 custom function 13?

I just bought an Elan 7. Page 89 of the manual refers to a custom

function 13 which allows various settings of the AF stop, AF start,

AE lock during metering, etc. It says these function can be

attributed to the Lens AF stop button. Can someone tell me which

button this is? I've read the manual twice and either I'm

overlooking this button, or it goes by a different name.

 

Thanks in advance.

<p>That button only exists on a few of the high-end lenses (the IS superteles - 300/2.8, 400/2.8, 500/4, 600/4 - and maybe one or two others). You can safely ignore CF13 unless you end up buying one of these lenses :-)</p>