Some devices like the Nook and the iRex DR800SG don't allow you to view our indexes in a nice collapsed form so you choose an airport then choose an approach. They instead show ALL the approaches and the airports. This makes the index very long. The 'Minimal' option removes the individual approaches and just lists the airport names(and if an airport has more than 10 approaches, it also adds a link for every 10 pages).
And if you want no airport index of one type or another(or both) you can turn them off by choosing 'None'
Which index first allows you to set your preferred index first.