minor doc tweaks.

Author: agentzh

lib/ngx/balancer.md

@@ -171,7 +171,7 @@ just specify the `nil` value for the corresponding argument (like the `connect_t
 
 Zero and negative timeout values are not allowed.
 
-You can specify millisecond precision by using floating point numbers like 0.001 (which means 1ms).
+You can specify millisecond precision in the timeout values by using floating point numbers like 0.001 (which means 1ms).
 
 Returns `true` when the operation is successul; returns `nil` and a string describing the error
 otherwise.

lib/ngx/semaphore.md

@@ -218,7 +218,7 @@ sema:post(2) -- releases 2 resources
 [Back to TOC](#table-of-contents)
 
 wait
-------------
+----
 **syntax:** *ok, err = sema:wait(timeout)*
 
 **context:** *rewrite_by_lua*, access_by_lua*, content_by_lua*, ngx.timer.**
@@ -237,6 +237,8 @@ When the `timeout` argument is 0, it means "no wait", that is, when there is no
 "resources" for the current running "light thread", this `wait` function call returns immediately
 `nil` and the error string `"timeout"`.
 
+You can specify millisecond precision in the timeout value by using floating point numbers like 0.001 (which means 1ms).
+
 "Light threads" created by different contexts (like request handlers) can wait on the
 same semaphore instance without problem.