How to stop this from happening in configuration?

I have a part file called spacer.  I set up different configuration to show different length. (The part is like a ruler with 10mm in thickness).  I use this part quite a lot in my assembly.

Recently I had a problem in my assembly that the part changed its configuration.  This is what I found. I use this part on assembly A and B.  If I change the configuration to 50mm on A, B will reflect that change when I open B.  Is there a way to stop SW from doing that?  What other option do I have?  I really don't want to create different part number just to show different sizes.

Message was edited by: Chika CoPart file is attached

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