If I ask to have something down "within a day" I mean 24 hours from now - today is day 0 and tomorrow is day 1, the day that it is due. So "within 7 days" means it is due on day 7, counting today as day 0.

Does within 30 days include the first day?

Within 30 days means within any duration of time less than or equal to 30 days (measured from some starting point). The following would all meet the requirement of within 30 days: 1 day, 3.14159265358979...

Does Within Include before?

Within is a single word. In the sense of your example, it means something like during, or before the end of: do not drink or eat during the hour before or the hour after you take these pills. ... Edited to point out that it applies to the hour before as well as the hour after.