I am not sure if this bug is in older versions, but in the latest Bambu Studio version 1.8.2.56, after a model is scaled, say to 200% (doubling its original size), when later one wants to come back to scale some more, the scale menu will show the already scaled model as 100%, ie. treating the scaled size as the new original size.
It will be more helpful to keep and show the scale percentage, in the above example, 200%, to make it easier for users to know how much more to scale to, and what the final scale percentage is in the end.