When an Electronics Technician is given the RMS value of a waveform other than a square wave, and wants to know the Peak-to-Peak equivalent, he or she multiplies the RMS value by twice the square root of two.
Applying this to a RMS Wavefront Error of 0.0721 gives:  0.0721 * 2 * 1.4142 = 0.2008 the Average Peak-to-Valley fraction of the specified wavelength of light for the test. Unfortunately, the worst case Peak and worst case Valley are lost in the average.

Now the wavelength of light used for the test is given as 633 nanometers, which is a deep visible Red that is longer than the Yellowish-Green light at 550 nanometers where our vision peaks. The actual measurement of the wavefront error is then 0.2008 of 633e-9 = 127.118e-9 meters or 0.1271 micrometers. Expressed as a fraction of light at 550 nanometers, this works out to 127.118e-9 / 550e-9 = 0.2311, which is approximately 10/43 as a common fraction that can be reduced to 1/4.3 or 1/4 by rounding off the denominator.  Thus an RMS Wavefront Error of 1/14 @ 633 nanometers equals a Peak-to-Valley Wavefront Error of 1/4 @ 550 nanometers.