diff --git a/CodeEntropy/config/arg_config_manager.py b/CodeEntropy/config/arg_config_manager.py
index 607bf36..89987b4 100644
--- a/CodeEntropy/config/arg_config_manager.py
+++ b/CodeEntropy/config/arg_config_manager.py
@@ -25,7 +25,12 @@
     },
     "end": {
         "type": int,
-        "help": "Stop analysing the trajectory at this frame index",
+        "help": (
+            "Stop analysing the trajectory at this frame index. This is "
+            "the frame index of the last frame to be included, so for example"
+            "if start=0 and end=500 there would be 501 frames analysed. The "
+            "default -1 will include the last frame."
+        ),
         "default": -1,
     },
     "step": {
diff --git a/CodeEntropy/main_mcc.py b/CodeEntropy/main_mcc.py
index e3cdc61..caeadb8 100644
--- a/CodeEntropy/main_mcc.py
+++ b/CodeEntropy/main_mcc.py
@@ -127,13 +127,17 @@ def main():
     if step is None:
         step = 1
     # Count number of frames, easy if not slicing
+    # MDAnalysis trajectory slicing only includes up to end-1
+    # This works the way we want it to if the whole trajectory is being included
     if start == 0 and end == -1 and step == 1:
+        end = len(u.trajectory)
         number_frames = len(u.trajectory)
     elif end == -1:
         end = len(u.trajectory)
-        number_frames = math.floor((end - start) / step) + 1
+        number_frames = math.floor((end - start) / step)
     else:
-        number_frames = math.floor((end - start) / step) + 1
+        end = end + 1
+        number_frames = math.floor((end - start) / step)
     logger.debug(f"Number of Frames: {number_frames}")
 
     # Create pandas data frame for results