USB booting :: syslinux.cfg

It seems to me that I remember a while back there were questions about editing the syslinux.cfg file in a usb boot system. There are several lines that appear the same. I would assume to edit the first one, but it seems that I remember someone in the past said this was wrong. I don't remember which line it was suggested should be edited.

Can anyone shed any light on this? I may be having an elderly moment.

David