Displaying rulers also shows sizes of positions, margins and spaces between rows and columns. These parameters can be changed by double-clicking their values on the ruler. Spaces between rows and columns can be also adjusted this way, unless it is required for all of them to be equal. Buttons with lock symbols indicate (and make it possible to set), if these spaces will change according page bleed. If the lock is locked it indicates that a value is set manually and will not change automatically according to page bleed. For example for imposition type booklet the gap must be constant in the saddle (usually zero).
Values shown in red suggest that the resulting sheet is smaller than is the minimum size for the imposition and show the difference between the sheet size and imposition margin.