Hi Val - are you talking about the control points of the trimmed face being larger than the edges?

That's actually a normal thing if you trim a face from a larger surface, the original surface is still a part of that face, it is the "underlying surface", there are just new trim curves on it.

There is some description on how underlying surfaces work here.

It is possible to shrink the underlying surface down if you want - to do that set up a shortcut key with this as the command: ShrinkTrimmedSrf

Then if you select that face and hit that shortcut key, that will shrink down the underlying surface to the trimming boundaries.

Please let me know if you are talking about something else other than that...

- Michael