diff --git a/DOCS/man/en/options.rst b/DOCS/man/en/options.rst
index 6299894b7a..5e64c641db 100644
--- a/DOCS/man/en/options.rst
+++ b/DOCS/man/en/options.rst
@@ -321,6 +321,12 @@
     from slow media, but can also have negative effects, especially with file
     formats that require a lot of seeking, such as mp4. See also ``--no-cache``.
 
+    Note that half the cache size will be used to allow fast seeking back. This
+    is also the reason why a full cache is usually reported as 50% full. The
+    cache fill display does not include the part of the cache reserved for
+    seeking back. Likewise, when starting a file the cache will be at 100%,
+    because no space is reserved for seeking back yet.
+
 --cache-pause=<no|percentage>
     If the cache percentage goes below the specified value, pause and wait
     until the percentage set by ``--cache-min`` is reached, then resume