docu update

actions/ost-compare-structures

@@ -118,8 +118,8 @@ def _ParseArgs():
         type=int,
         help=("Only has an effect if model is in mmcif format. By default, "
               "the assymetric unit (AU) is used for scoring. If there are "
-              "biounits defined in the mmcif file, you can specify the index "
-              "of the one which should be used."))
+              "biounits defined in the mmcif file, you can specify the "
+              "(0-based) index of the one which should be used."))
 
     parser.add_argument(
         "-rb",
@@ -130,8 +130,8 @@ def _ParseArgs():
         type=int,
         help=("Only has an effect if reference is in mmcif format. By default, "
               "the assymetric unit (AU) is used for scoring. If there are "
-              "biounits defined in the mmcif file, you can specify the index "
-              "of the one which should be used."))
+              "biounits defined in the mmcif file, you can specify the "
+              "(0-based) index of the one which should be used."))
 
     parser.add_argument(
         "-rna",