<bg-layer> = <bg-image> || <position> [ / <bg-size> ]? || <repeat-style> || <attachment> || <box>{1,2}

If one <box> value is present, then it sets both 'background-origin' and 'background-clip' to that value. If two <box> values are present, then the first sets 'background-origin' and the second 'background-clip'.

<bg-layer> = <bg-image> || <position> [ / <bg-size> ]? || <repeat-style> || <attachment> || <box>{1,2}

If one <box> value is present, then it sets both 'background-origin' and 'background-clip' to that value. If two <box> values are present, then the first sets 'background-origin' and the second 'background-clip'.