Column Margins wrong

Im trying my hand at ‘strips’. When I add columns to the strip, the column margins are different to the page margins. Why is that? Ive searched the strip settings and cannot adjust the column margins to conform with the rest of the page. Can someone point me in the right direction please.

Ive just noticed that the column margins come right when the strip is set on ‘page’ layout. I had it on ‘stretch’ across screen. So, before I boot it off ‘stretch’ could someone tell me the purpose of the ‘stretch’ option?