You can customize the grid in the background of the RFEM work plane. To do this, click the button to open the "Work Plane and Grid/Snap" dialog box. Among other things, you can adjust the grid point spacing there, which should be based on the size of the structure to be entered.
Click to get to a dialog box where you can define the units and decimal places for the entire model.
For the splice entry, the unit for lengths has been changed to cm and the grid point spacing was set to 1 cm. Furthermore, the grid was placed in the XZ plane.