I realize this is an old post, but wanted to offer an answer for others that may run across it with the same question.
The Work Item State Codes are not user configurable. They are used to show the current state of a work item's workflow. Aegis saves the state of all work items so that in the case of an interruption in service (such as a power outage), it will start back up in its previous state with all existing work items.
In the latest version of Aegis, here is a list of possible states and their corresponding ID: