netmeg - 4:21 pm on Mar 26, 2013 (gmt 0)
That setting applies to all of your ad units, all sizes, sitewide.
UNLESS you overrode it in a saved ad style. If your saved ad styles use the default settings, then that is correct.
But if you saved a specific size in an ad style (which I have done for some sites) then you need to change it there - not in the ad, but in the ad style (which is under My Ads and then over on the left, Ad Styles)