By default, PhoneBurner is going to sort your contacts based on the date they are added to the system. For example, when you import your contacts list, whoever is at the top of the list was added first and will appear first. You can change this if you'd like.
Sort by Last Call
This allows you to change the order of your contacts based on the last time they were called using PhoneBurner. You can sort them in 2 directions. 9 over 1 - Which will start with the contacts that you most recently called in the current view (folder or search). 1 over 9 - which will start with the contacts that you haven't called or it has been the longest since you called them in the current view. Refresh your list after each session and the contacts you just called will be moved to the end of the list and contacts you haven't called or it has been the longest since they were called move up to the top of the list.
Sort by Times Called
This option allows you to change the order based on the total times the contacts have been called using PhoneBurner. Similar to option 1, but rather than focusing on when they were called, PhoneBurner focuses on the number of times they've been called.