If a court or compensation authority sets a date for the hearing to determine the claim for compensation:
(a) an extension under section 18 or 19 must not be granted after the day on which the date for the hearing was set; and
(b) any extension that:
(i) was granted before the date for the hearing was set; and
(ii) would, apart from this section, have extended the period in question beyond 28 days after the day on which the date for the hearing was set, or beyond the date set for the hearing;
is taken to be an extension of the period until 28 days after the day on which the date for the hearing was set, or until the date set for the hearing, whichever occurs earlier.