O to 1 should be fine. Assume this is a percentage identified by your programmer?? Voltage fluctuations and engine vibrations will have the readings float a bit.
The pcm will actually adapt to the closed throttle position with "key on" in the ignition.
The myth is it needs to be adjusted to .99 volts for best performance. This simply is not true base on the above statement. It should fall between .95-.99 volts. You should keep it below 1v though or it may exceed the design limits with voltage fluctuations causing idle issues. Unless you modify it or tamper with the throttle stop screw this should not be an issue.