diff --git a/data/self_supervised_temporal_labeled_mask_online_dataset.py b/data/self_supervised_temporal_labeled_mask_online_dataset.py
index 8174a3654..ace282629 100644
--- a/data/self_supervised_temporal_labeled_mask_online_dataset.py
+++ b/data/self_supervised_temporal_labeled_mask_online_dataset.py
@@ -61,24 +61,37 @@ def __init__(self, opt, phase, name=""):
 
         self.A_size = len(self.A_img_paths)  # get the size of dataset A
 
+        # dataset form img(bbox)/vid_series/vid_series_#frame.png(.txt)
+        # Dict to track the number of frames in each video series
         self.frames_counts = OrderedDict()
         for path in self.A_img_paths:
             vid_series_paths = os.path.dirname(path)
+            # If this video series path hasn't been processed yet, initialize it in frames_counts.
+            # The value is a tuple (count, count_minus), where:
+            # - 'count' will store the number of frames in the series.
+            # - 'count_minus' is calculated as a negative offset based on the number of frames and step size.
+            # This offset acts as a limit to determine which frames to choose from the series.
             if vid_series_paths not in self.frames_counts:
                 self.frames_counts[vid_series_paths] = (
                     0,
                     -self.num_frames * self.frame_step,
                 )
+            # Retrieve the current count and count_minus for the video series.
             count, count_minus = self.frames_counts[vid_series_paths]
             count += 1
+            # Update frames_counts with the new count and recalculate count_minus.
+            # Count is the total number of frames in the video series
+            # count_minus is the number of available frames in this video series
             self.frames_counts[vid_series_paths] = (
                 count,
                 count - self.num_frames * self.frame_step,
             )
-
+        # Store cumulative sums of available frames in the order of video series.
         self.cumulative_sums = []
         cumulative_sum = 0
+        # Create a list of video series paths for tracking later
         self.vid_series_keys = list(self.frames_counts.keys())
+        # Iterate through each video series in frames_counts to compute the cumulative sum of available frame.
         for _, (_, count_minus) in self.frames_counts.items():
             if count_minus > 0:
                 cumulative_sum += count_minus
@@ -98,29 +111,29 @@ def get_img(
         if len(self.frames_counts) == 1:  # single video mario
             index_A = random.randint(0, self.range_A - 1)
         else:  # video series
-            range_A = sum(
-                count_minu
-                for count, count_minu in self.frames_counts.values()
-                if count_minu > 0
-            )
-            index_A = random.randint(0, range_A - 1)
-            selected_index = bisect.bisect_right(self.cumulative_sums, index_A)
-            selected_key = self.vid_series_keys[selected_index]
-            path_num = (
-                index_A - self.cumulative_sums[selected_index - 1]
-                if selected_index > 0
-                else 0
-            )
+            range_A = self.cumulative_sums[
+                -1
+            ]  # total number of frames that can be used as a starting frame
+            random_A = random.randint(
+                0, range_A - 1
+            )  # chose one frame from available video series
+
+            # according to the selected_index, get the video series and frame number
+            selected_index = bisect.bisect_left(self.cumulative_sums, random_A)
+            selected_vid = self.vid_series_keys[selected_index]
+            if selected_index > 0:
+                frame_num = random_A - self.cumulative_sums[selected_index - 1]
+            else:
+                frame_num = random_A
+
             filtered_paths = [
                 path
                 for path in self.A_img_paths
-                if os.path.dirname(path) == selected_key
+                if os.path.dirname(path) == selected_vid
             ]
-            if path_num < len(filtered_paths):  # this is absolu true
-                selected_path = filtered_paths[path_num - 1]
-            else:
-                print("Path number exceeds available paths in the selected directory")
 
+            # Get path and index_A
+            selected_path = filtered_paths[frame_num - 1]
             index_A = self.A_img_paths.index(selected_path)
 
         images_A = []