The docstring of EpochsArray says for the data parameter “see notes for proper units of measure.” The notes then tell you that you should use unit V for EEG data. It sounds like you are passing it data in μV instead. Don’t do that.
FYI, in MNE-Python everything is stored in SI units. Sometimes our plotting functions will convert the units before plotting, just so that the axis labels don’t range from say 0.000001 to 0.000006 V, but instead from 1 to 6 μV. Again this is only on the plot, the underlying data object still stores the numbers in SI units. This is documented here: Algorithms and other implementation details — MNE 1.2.2 documentation