  Here we consider the results of direct measurements of muons in extensive air
showers with zenith angles $\theta \le 45^{\circ}$ and energy above $10^{17}$
eV, obtained at the Pierre Auger Observatory and Yakutsk array. In both
experiments muons were registered with underground scintillation detectors with
$\approx 1.0 \times \sec\theta$ GeV energy threshold. Measured density values
were compared to theoretical predictions calculated within the framework of the
QGSJet-II.04 hadron interaction model. They differ by factor $1.53 \pm
0.13$(stat). We demonstrate that this difference is due to overestimation of
muon densities by 1.22 times and underestimation of primary energy by 1.25
times in the Auger experiment.
