How are your buttons wired up? Normally, one side it tied to ground and the other side it tied to the input pin with the pin configured to have the internal pullup resistor enabled. If this is the case, when the button state is HIGH, it means the button is NOT pressed. Your logic is the opposite of that.
Also, the way your code is will cause one button press to increment/decrement the setpoint many times since you will go back through the loop() To a human, a single button press of ~ 1/2 a second will look like hundreds of button presses to your code. You should only sample the buttons once in a while or wait for the button to be released or use a button library that handles this and debouncing, etc.