docs: improve borg check --max-duration description

src/borg/archiver.py

@@ -3362,15 +3362,18 @@ def define_borg_mount(parser):
         The ``--max-duration`` option can be used to split a long-running repository check
         into multiple partial checks. After the given number of seconds the check is
         interrupted. The next partial check will continue where the previous one stopped,
-        until the complete repository has been checked. Example: Assuming a full check took 7
+        until the complete repository has been checked. Example: Assuming a complete check took 7
         hours, then running a daily check with --max-duration=3600 (1 hour) resulted in one
-        full check per week.
+        completed check per week.
 
-        Attention: Partial checks can only do way less checking than a full check (only the
+        Attention: A partial --repository-only check can only do way less checking than a full
-        CRC32 checks on segment file entries are done), and cannot be combined with the
+        --repository-only check: only the non-cryptographic checksum checks on segment file
-        ``--repair`` option. Partial checks may therefore be useful only with very large
+        entries are done, while a full --repository-only check would also do a repo index check.
-        repositories where a full check took too long. Doing a full repository check aborts a
+        A partial check cannot be combined with the ``--repair`` option. Partial checks
-        partial check; the next partial check will restart from the beginning.
+        may therefore be useful only with very large repositories where a full check would take
+        too long.
+        Doing a full repository check aborts a partial check; the next partial check will restart
+        from the beginning.
 
         The ``--verify-data`` option will perform a full integrity verification (as opposed to
         checking the CRC32 of the segment) of data, which means reading the data from the