Some customers use specific functionality that only returns the "status text" and not the "status" which only shows up in the statistics. To set a new "status" you will need to define a user return code and modify the UC_ZUTYP table.
For more information on this fuctionality, please check out the documentation under User Guide--> Objects--> Working with Objects--> Return Codes--> User Return Codes of Executable Objects.
But, again, this only shows up the the statistics, not the Activities Window.
In Automic Operations Manager (6.00A & 8.00A) and Automic Automation Engine (9.00A) you cannot change the pre-set statuses with user-defined statuses. While you can change 'ENDED_OK" to "ENDED_LOST" or some other Automic default status, you cannot enter something like "ENDED_155."