Grid coordinates and snapping to grid points
The coordinates reported in the status bar are the coordinates of the cursor position on the current grid. These are referred to as the grid coordinates. The grid coordinates are reported in the current grid axes (and global axes, if these differ).
Snap to grid may be set by giving the Sculpt > Snap to grid points (Ctrl+Alt+S) menu command (also available on the Sculpt toolbar). When this is set on, the grid coordinates are the coordinates of the nearest grid point or intersection of grid lines on the current grid. Otherwise, the accuracy of the grid coordinates is based on the screen resolution and the structure scale.
Note: When the construction grid is normal to the picture plane then no coordinates are reported in the status bar.