Hi Vishnu,
All of the inputs to the PID Express VI are 16 bit inputs. In the example, the setpoint and process variables are ranges from 0 to 100%, so the setpoint is set relative to the process variable maximum. The help for the Express VI for the PID Gains says "the upper 8 bits (out of 16) of each integer represent the integer portion of the gain", meaning that 128 is the highest (unscaled value, scaled would be 32767) value you can specify for Kc.
Regards,
James R.
National Instruments