Enter 10 followed by [TAB] for an attenuation of 10 dB.
Enter 5 [TAB] for a power of 5 watts.
Enter 0.5 [TAB] for resistors of 1/2 watt or 0,5 in non English versions of Excel.
Use the numeric keypad for the comma or point.
When you see #### please use a comma instead of a point or the other around.
The calculator first calculates the power that is dissipated in each of the 3 compound resistors R1, R2, and R3. The power determines the number of resistors in parallel that should be used.