admob – GoogleAdMob Unity banner must not consume more than 60% of landscape screen width on any device

I have a question regarding the GoogleAdMob Unity banner.
I need to show a banner on the top center of the screen. The Top “Right” and “Left” sides of the screen have UI which can’t be overlapped by the banner. If I use a smart banner this will take the complete landscape width, but if I use standard banner AdSize.Banner gives which gives (320×50)dp is not taking the complete width on my testing device with testing ads.
Should I consider the standard banner with (320×50)dp for landscape half-width of the screen? Banner must not consume more than 60% of landscape screen width on any device.