Hi Hans,
That is perfectly normal... That is to say, you got exactly what you've asked for.
When you create a box using Applescript, Quark asks you to supply it with bounds in the form of
{Top, Left, Bottom, Right}
However the values shown in the measurements palette are in the form
{X(origin), Y(origin), W(idth), H(eight)}
Now if you translate your bounds ({"9 cm", "2.123 cm", "14 cm", "8"}) to what should be returned by your measurements palette you get:
X: 2.123 cm
Y: 9 cm
W: 5.877 cm (Right - Left or 8 - 2.213)
H: 5 cm (Bottom - Top or 14 - 9)
Hope this helps!