Not sure what you mean by is it understood by the application, but we have an application where in we budget similarly & have open periods from Sept FY12 to Dec FY13. Yes your budget scenario should be set from AUG 2012 to DEC 2012.
Just to confirm that you wrote it by mistake in the last sentence in your reply. You meant "Yes the budget scenario should be set from Aug 2012 till Dec 2013"...is this right ?? as you wrote it from Aug 2012 till Dec 2012.