Add explanation for code

sohstationviewer/model/reftek_data/reftek_reader/core.py

@@ -89,8 +89,14 @@ class DecimatedReftek130(obspy_rt130_core.Reftek130):
         if data[0]['data_format'] == b'16':
             data_points = data['payload'][:, :2]
             # The data is stored in a big-endian order.
+            # Merge the two bytes in each data point into a two-byte number.
             data_points = data_points.view(np.dtype('>i2'))
-            data_points = data_points.astype(np.dtype('>i4')).view('>u1')
+            # Sign extend the two-byte numbers into four-byte numbers. This is
+            # done to match the byte length of other data formats.
+            data_points = data_points.astype(np.dtype('>i4'))
+            # Convert each four-byte number into four bytes to match Obspy's
+            # payload format.
+            data_points = data_points.view('>u1')
         else:
             if data[0]['data_format'] in [b'C0', b'C1', b'C2', b'C3']:
                 # The first 40 bytes in the payload are filler, so we skip past