diff --git a/swh/storage/in_memory.py b/swh/storage/in_memory.py
--- a/swh/storage/in_memory.py
+++ b/swh/storage/in_memory.py
@@ -99,7 +99,7 @@
         }
 
         if with_data:
-            summary['content:bytes:add'] = count_content_bytes_added
+            summary['content:add:bytes'] = count_content_bytes_added
 
         return summary
 
diff --git a/swh/storage/storage.py b/swh/storage/storage.py
--- a/swh/storage/storage.py
+++ b/swh/storage/storage.py
@@ -208,7 +208,7 @@
             Summary dict with the following key and associated values:
 
                 content:add: New contents added
-                content:bytes:add: Sum of the contents' length data
+                content:add:bytes: Sum of the contents' length data
                 skipped_content:add: New skipped contents (no data) added
         """
         content = [dict(c.items()) for c in content]  # semi-shallow copy
@@ -257,7 +257,7 @@
             # transaction, bubbling up any exception
             content_bytes_added = added_to_objstorage.result()
 
-        summary['content:bytes:add'] = content_bytes_added
+        summary['content:add:bytes'] = content_bytes_added
         return summary
 
     @db_transaction()
diff --git a/swh/storage/tests/test_storage.py b/swh/storage/tests/test_storage.py
--- a/swh/storage/tests/test_storage.py
+++ b/swh/storage/tests/test_storage.py
@@ -558,7 +558,7 @@
         actual_result = self.storage.content_add([cont])
         self.assertEqual(actual_result, {
             'content:add': 1,
-            'content:bytes:add': cont['length'],
+            'content:add:bytes': cont['length'],
             'skipped_content:add': 0
         })
 
@@ -580,7 +580,7 @@
         actual_result = self.storage.content_add([cont, cont])
         self.assertEqual(actual_result, {
             'content:add': 1,
-            'content:bytes:add': cont['length'],
+            'content:add:bytes': cont['length'],
             'skipped_content:add': 0
         })
 
@@ -591,7 +591,7 @@
         actual_result = self.storage.content_add([cont, cont2])
         self.assertEqual(actual_result, {
             'content:add': 2,
-            'content:bytes:add': cont['length'] + cont2['length'],
+            'content:add:bytes': cont['length'] + cont2['length'],
             'skipped_content:add': 0
         })
 
@@ -602,7 +602,7 @@
 
         self.assertEqual(actual_result, {
             'content:add': 1,
-            'content:bytes:add': cont['length'],
+            'content:add:bytes': cont['length'],
             'skipped_content:add': 0
         })
 
@@ -738,7 +738,7 @@
 
         self.assertEqual(actual_result, {
             'content:add': 0,
-            'content:bytes:add': 0,
+            'content:add:bytes': 0,
             'skipped_content:add': 2,
         })
 
@@ -780,7 +780,7 @@
 
         self.assertEqual(actual_result, {
             'content:add': 0,
-            'content:bytes:add': 0,
+            'content:add:bytes': 0,
             'skipped_content:add': 2,
         })