By default, Load Manager will create load numbers for you automatically, depending on the Starting Load Number. You can change your Starting Load Number in the Settings menu.
In the Settings menu you can change your Starting Load Number, as well as access another feature - the "Allow Load Number Entry" feature.
Turning on "Allow Load # Entry" allows you to enter your own load number for every load. If you do not enter a load number, Load Manager will create on for you based on your Starting Load #.