These notes aren't correct. The options should be:
`$max_width !== null && $max_height !== null` "150 x 120 px"
`$max_width === null && $max_height !== null` "120 px high"
`$max_width !== null && $max_height === null` "120 px wide"
`$max_width === null && $max_height === null` "" (no max-dimensions)