Stereo Calibration RMS and epipolar error

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Hello, i have run the opencv stereo_calib simple for my images , the program found 8 pairs and show me :

...........8 pairs have been successfully detected. Running stereo calibration ... done with RMS error=39.3507 average epipolar err = 67.3832

i want to ask about error value is that good for reconstrcution or not? if not please how i can reduce the error Thank you