There is obviously more to this than meets the eye....If you insert a drawing into another drawing that has a STANDARD dimstyle, apparently it changes that drawings settings. This has to be a good reason not to use this style at all. Maybe you need one that is unique to yourself-that way you would always be sure it would not get messed up.
I also neglected to say that my example is METRIC - ie 3 means 3mm which is 1/8 ".
The use of annotation scale adds another layer of complexity to it all.
Maybe I should retire now before it becomes all too hard!