Look at the production xml and see if that value if defined there. Sometimes if you happen to save an empty value from the production page it'll put the xml tag in there. Once that is there, the system default settings will not override that value.

I am unfamiliar with being able to remove that besides removing it from the production xml itself.

You implement DSTIME on a class by doing the following in your persistent class:

Parameter DSTIME As STRING [ Constraint = ",AUTO,MANUAL", Flags = ENUM ] = "AUTO";

You will need to implement batching as well so you only pick up changes to a class from the last time you queried against DSTIME. I believe there are a few posts in the community that further discuss implementing DSTIME. 

Best of luck.