sagrada mitra records

I have read but can't seem to understand how to use the numbering system for la Sagrada Mitra records. I have tried to follow the instructions but am getting nowhere. Can someone please simplify them for a dummy like me??
Getting into the ones that give you the page number is easy but getting into the ones that have numbers larger than the number of pages in the file seems impossible for me.. Help..
Linda Castanon-Long