Understanding Left + Bottom columns for Page Boxes in Inspector

[prepressman_ntsf]

When dealing with page box conundrums oftentimes there will be some pages in a document that might have different variables for width and height. Likewise there may be differing numbers for the Left and Bottom columns.

What do increments in the Left and Bottom columns represent and how do they affect the document's page boxes?

[loicaigon]

You are just looking at the origin of the mediabox with other page boxes being shifted from mediabox origin.
The values could be all the same if all page boxes would be set on the media box. But more than often, you have different props for the page boxes.
For example, a Bleedbox being bigger than the trim and the Mediabox being bigger than the Bleedbox.