Fallback method for fonts is unclear

A fifth fallback method exists for fonts that have been embedded using the @font-face mechanism. When using such fonts, the basic rules of CSS are used to provide fallback information. There is no requirement to add fallback data to the manifest entries for embedded fonts. As an example, the following CSS is considered to have sufficient fallback information:

@font-face {
font-family: "My Font";
src: url("fonts/MyFont.otf")
}
p { font-family: "My Font", serif }