Sorry for irritating, i wanted to say the X and Y Scale was different.
I am an pain patient who needs his daily painkiller dose and sometimes i confound things.
X and Y scale is harmless aside from visually making the table look funny.
They should be 1 and 1 for an absolutely proper appearance
( put a perfect circle on the playfield, now adjust X or Y and watch what happens to the circle)
But a lot pf people change them because they can not bear to have unfilled pixels on the screen.
It is harmless aside from the visual aspects and egging of the ball.
And yes, a lot of tables come with a modified X and Y scale.
Personally, i stick them back to 1 and 1, then adjust the Z offset until one of the tables dimensions hits the sides of the screen
and then that is it, what ever is empty space in the other dimension, well it is just empty space is all, it if really annoys me i will edit the table and put something in the empty space, Side rails, a lockdown bar, a Beer advertizement at the top of the table, etc but usually i just leave it be.
I prefer some unused screen to distorting the ball and the graphics that the artist spent so much time on 
but Z scale, that one you dont want to change
Try it some time, with out saving the table
make the zscale 0.5 and launch the table
then make it 4.0 and launch the table
See how fubar the table is physically?