Motorola dct dvr 6416 111 Custom 1 Custom 2 Custom 3 and 1,2,3--ABC?

This is my first experience with a dvr, didn't get an instruction book when I got it a week ago.  There is still something I haven't figured out how to use, or what it's for.  In guide, sort,...custom123, is that for storing some channels to go to quickly?  How do you put the channels into each custom. All I see in Set Up is, all channels or favorite channels.

Is 1 2 3,  ABC for selecting channel letters or numbers in the guide?   Does it have a paper instruction guide that explains it all?

Thanks for reading,