added note

Author: teonbrooks

mne/io/cnt/cnt.py

@@ -328,8 +328,12 @@ def _get_cnt_info(input_fname, eog, ecg, emg, misc, data_format, date_format, he
         lowpass_toggle = bool(np.fromfile(fid, "i1", count=1).item())
         highpass_toggle = bool(np.fromfile(fid, "i1", count=1).item())
 
+        # Reference: https://paulbourke.net/dataformats/eeg/
         # Header has a field for number of samples, but it does not seem to be
         # too reliable. That's why we have option for setting n_bytes manually.
+        # According to link above, the number of samples should be calculated as follows:
+        # nsamples = SETUP.EventTablePos - (900 + 75 * nchannels) / (2 * nchannels)
+        # where 2 likely refers to the data format with default 2 bytes.
         fid.seek(_NSAMPLES_OFFSET)
         n_samples = np.fromfile(fid, dtype="<u4", count=1).astype(int).item()
         n_samples_header = n_samples