Fix typo: "ofbytes" should be "of bytes"
diff --git a/Doc/library/io.rst b/Doc/library/io.rst
index 5a2de14..c6605c8 100644
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -361,9 +361,9 @@
 
    .. method:: readinto(b)
 
-      Read up to len(b) bytes into bytearray *b* and return the number ofbytes
-      read.  If the object is in non-blocking mode and no bytes are available,
-      ``None`` is returned.
+      Read up to len(b) bytes into bytearray *b* and return the number
+      of bytes read.  If the object is in non-blocking mode and no
+      bytes are available, ``None`` is returned.
 
    .. method:: write(b)