is it possible that your data were recorded in nanovolts?
raw = mne.io.read_raw_edf("Irina_artifacts_test.edf")
raw.load_data()
raw.apply_function(lambda x: x * 1e-9)
raw.plot()
Note also that your raw.info says that your sampling rate was 500Hz and your highpass frequency was 1000Hz. That’s probably wrong (I don’t think MNE-Python will even allow a high-pass cutoff that is higher than the sampling frequency)