Issue #19795: Improved more markups of True/False.
diff --git a/Doc/c-api/number.rst b/Doc/c-api/number.rst
index 9bcb649..4a2d931 100644
--- a/Doc/c-api/number.rst
+++ b/Doc/c-api/number.rst
@@ -278,5 +278,5 @@
 
 .. c:function:: int PyIndex_Check(PyObject *o)
 
-   Returns True if *o* is an index integer (has the nb_index slot of  the
-   tp_as_number structure filled in).
+   Returns ``1`` if *o* is an index integer (has the nb_index slot of  the
+   tp_as_number structure filled in), and ``0`` otherwise.