GGU-SLAB: Step 6: Assign slab material (Example 1)
Go to the "System/Slab material" menu item.

Enter the values given in the dialog box. The numerical input for d(1)top, d(2)top, d(1)bottom and d(2)bottom are only important for subsequent slab reinforcement. This defines the distance of the centroid of the reinforcement from the upper and lower slab surface for the principal directions of reinforcement 1 and 2.