As I learned myself, that message is simply saying that the build has reached and is being maintained at the set temperature. It won't and shouldn't stop unless intentionally disabled in Escribe.
If you haven't done that, it will continue to display and that is by design.
If you want it to go away, you need to do what the fella told me above. Connect your mod to Escribe, go into the screen dialog and disable that message.
It might be slightly different for the 250C, but I'm sure the general principle is the same.