This is very weird.
1) I draw a rectangle with the rectangle tool (M). I press option, then click, input a width and height of 50mm.
2) I apply a stroke of 1pt to that rectangle.
Result: The dimensions (w, h) now show 65.353.
For as long as I can remember this has never been handle this way. The rectangles dimension should be untouched by applying a strok to it.
I'm using Version 14.0.0 on OS X 10.5.7.
You probably toggled "use preview bounds" on - it will give you the measurement including your stroke, which by default, straddles the 50mm dimension you created.
Look in the flyout menu of your align panel.
Jeez... I have *never* used that option.
I must have checked it off without thinking in the Gerneral preferences.
Thanks for your help!