You can adjust the grid formatting in the Graphical Column Schedule. On the Properties palette, under the Graphics section, click the Grid Appearance Edit button.
For Column Locations: Width of the Column Locations columns.
For Level Names: Width of the Level heading column.
Above Top Level: Margin above the top level.
Below Bottom Level: Margin below the bottom level.
Between Segments: The minimum space between schedule segments.
Adjust the properties and click OK.