Fixed the "USAGE" to improve readability.

Author: t2-kob

UnixBench/USAGE

@@ -65,11 +65,12 @@ so that randomly-churning background processes don't randomise the results
 too much.  This is particularly true for the graphics tests.
 
 
-If you need to change the directories, use "Environment variables" about below.
+Output can be specified by using the following variables:
 
-  * "UB_RESULTDIR"        : Output destination path(absolute) of the result files.
-  * "UB_TMPDIR"           : Directory path(absolute) used for file I/O tests(named fs****).
-  * "UB_OUTPUT_FILE_NAME" : Output file name. If exists same file, it will be overwrite completly.
+  * "UB_RESULTDIR" : Absolute path of output directory of result files.
+  * "UB_TMPDIR" : Absolute path of temporary files for IO tests.
+  * "UB_OUTPUT_FILE_NAME" : Output file name. If exists it will be overwritten.
+    
 ============================================================================
 
 Tests