find: add unit for mtime

Clarifying that mtime stands for no. of days

pages/common/find.md

@@ -20,9 +20,9 @@
 
 - Find files using case insensitive name matching, of a certain size:
 
-`find {{root_path}} -size +500k -size -10MB -iname '{{*.TaR.gZ}}'`
+`find {{root_path}} -size {{+500k}} -size {{-10MB}} -iname '{{*.TaR.gZ}}'`
 
-- Delete files by name, older than a certain number of days:
+- Delete files by name, older than 180 days:
 
 `find {{root_path}} -name '{{*.ext}}' -mtime {{+180}} -delete`