Ramping Down the variable in Arduino IDE with the help of millis()??......

Projects Programming
14

That graph is more like:

setpoint = 0.04;
delay(2);
setpoint = 1.75;
delayMicroseconds(8500);  // 8.5 milliseconds
setpoint = 0.08;

Nothing on that graph looks anything like a 'ramp'. It sounds like you are confused about what it is you are trying to accomplish. Perhaps you should start with what the goal is and not jump into designing code until the specifications are clear.