fix up numbering typo in README

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: I8f005308bafcfd333664a411b578fc67e90fb47f
diff --git a/README.md b/README.md
index bb5c649..5cc15ef 100644
--- a/README.md
+++ b/README.md
@@ -520,13 +520,13 @@
 phosphor_log_manager_SOURCES += \
         extensions/foo/foo.cpp
 ```
-3. In `extensions/extensions.mk`, add the makefile include:
+4. In `extensions/extensions.mk`, add the makefile include:
 ```
 if ENABLE_FOO_EXTENSION
 include extensions/foo/foo.mk
 endif
 ```
-4. In the extension code, register the functions to call and optionally disable
+5. In the extension code, register the functions to call and optionally disable
    log capping using the provided macros:
 ```
 DISABLE_LOG_ENTRY_CAPS();