the document is right..

The type of phone specifies the number of call appearances like 8434 could have 34 call appearances .. I have not configured 84XX series of phones but had done this on 46XX and 54XX phones without any issues..

We have an button to toggle the call appearance button... in normal it may have 1 to 12, when toggled to right it may have 13 to 24 and on...