Conditional holidays are of the form :
where x and y combine to mean : if there are x holidays from the a-holidays today, then show the yth one here.
Using the above example, we see that if there is only one holiday, it will appear at the position of the [9Fi11] token (left sample below). If there are 2 holidays or more, the first one will replace the [9Fi21] token and the second will replace the [9Fi22] token (right sample below).
The tokens [9Fi3] and [9Fi4] are discussed in the topic on sequential holidays tokens.
See also : Specific Holidays Sets Modifier.