diff --git a/keras/utils/dataset_utils.py b/keras/utils/dataset_utils.py
index 35d234d6255..156cb3a2e48 100644
--- a/keras/utils/dataset_utils.py
+++ b/keras/utils/dataset_utils.py
@@ -33,17 +33,19 @@
 def split_dataset(
     dataset, left_size=None, right_size=None, shuffle=False, seed=None
 ):
-    """Split a dataset into a left half and a right half (e.g. train / test).
+    """Split a dataset into a left part and a right part (e.g. train / test).
 
     Args:
         dataset: A `tf.data.Dataset` object, or a list/tuple of arrays with the
           same length.
-        left_size: If float (in the range `[0, 1]`), it signifies
-          the fraction of the data to pack in the left dataset. If integer, it
-          signifies the number of samples to pack in the left dataset. If
-          `None`, it uses the complement to `right_size`. Defaults to `None`.
-        right_size: If float (in the range `[0, 1]`), it signifies
-          the fraction of the data to pack in the right dataset. If integer, it
+        left_size: If float (in the range `[0, 1]` (excluding the
+          boundary values 0 and 1)), it signifies the fraction of the data to
+          pack in the left dataset. If integer, it signifies the number of
+          samples to pack in the left dataset. If `None`, it uses the
+          complement to `right_size`. Defaults to `None`.
+        right_size: If float (in the range `[0, 1]` (excluding the
+          boundary values 0 and 1)), it signifiesthe fraction of
+          the data to pack in the right dataset. If integer, it
           signifies the number of samples to pack in the right dataset. If
           `None`, it uses the complement to `left_size`. Defaults to `None`.
         shuffle: Boolean, whether to shuffle the data before splitting it.
@@ -398,8 +400,8 @@ def _rescale_dataset_split_sizes(left_size, right_size, total_length):
         raise ValueError(
             "`left_size` should be either a positive integer "
             f"smaller than {total_length}, or a float "
-            "within the range `[0, 1]`. Received: left_size="
-            f"{left_size}"
+            "within the range `[0, 1]` (excluding the boundary values 0 and 1)."
+            f"Received: left_size = {left_size}"
         )
 
     # check right_size is non-negative and less than 1 and less than
@@ -413,8 +415,8 @@ def _rescale_dataset_split_sizes(left_size, right_size, total_length):
         raise ValueError(
             "`right_size` should be either a positive integer "
             f"and smaller than {total_length} or a float "
-            "within the range `[0, 1]`. Received: right_size="
-            f"{right_size}"
+            "within the range `[0, 1]` (excluding the boundary values 0 and 1)."
+            f"Received: right_size = {right_size}"
         )
 
     # check sum of left_size and right_size is less than or equal to