tween in Library

[tmc]

New to CS3, been using Flash a while - - -
Create a motion tween with the property window for a frame between 2 keyframes. It works, but creates a Library element named Tween 1 (or another number). That didn't use to happen and is bloating the library. How do I stop it?

[tmc]

seems that if you try to tween a symbol and there is something else in that layer, then tween # and tween # + 1 get created in the library

move one of the items to another frame and this doesn't happen

common mistake of selecting a shape fill, but not the stroke when converting to symbol