The Quartus® II software generates this warning message if you do not specify the time unit for your Classic Timing Analyzer assignments. For example, the assignment set_input_delay 0.500 -clk_ref clock -to data_in -max does not include the time unit for the number 0.500. In such cases, it is not clear whether the assignment is for ns or MHz.
Beginning with the Quartus II software version 6.0, you must specify the time unit in the assignment, such as set_input_delay 0.500ns -clk_ref clock -to data_in -max. The time unit is required to ensure that the correct setting is applied.
A future version of the Quartus II software may give a warning message about the timing unit requirement.