What is "prints true to size"?

I’ve been an OmniGraffle addict for at least a decade. I’ve always wondered about one line in the interface and I’m finally going to ask:

Canvas > Units > Ruler Units > “* prints true to size”

What does that mean?

Thank you!

– Sal

Only seems available for points, cm, and inches (fractional) and help manual has this statement:

“Ruler units followed by an asterisk ***** in the previous list means that these measurement types will print true to size when selected.”

I would guess from it means what you see in scale is ‘exactly’ what will be printed at those measurements. Default scale on all three goes to “1 x = 1 x”.

Kind of the new WYSIWYG?