One of the essential features of high-frequency components and systems is the adaptation of the ports. A vectorial network analyzer (VNA) is generally used to define them. With this, adjustments of 60 dB can readily be measured.
These high adjustment values are not measured because the VNA has even better values but rather because its systematic errors are calculated by calibration with a known calibration kit. However, the individual parts of the calibration kit also introduce uncertainties, which also limit the measurement accuracy. It is also questionable whether an adjustment of 60 dB is the true value.