fix typo in 6.

6_unix_processes.md

@@ -228,7 +228,7 @@ Only the *root* user can lower the **nice** value of a process. You can also sta
 nice -n 10 stress -c 1 -t 3600 &
 ```
 
-Without root access you can only set value higher than 0.
+Without root access you can only set value lower than 0.
 
 > We have seen the commands:
 >