The rules that use the category "<digit-pl>" are:

<flight_id-not_creatable-pl>

<flight_noun-pl> of <digit-pl> <specific_aircraft_type-pl>

<second_setting>

<digit-pl> <time_interval_unit-second-pl>

<degree_number-not_initial_zero-90-pl>

<digit-pl>

<degree_number-180-pl>

<digit-pl>

<up_to_two_digits-pl>

<digit> <digit-pl>

<minute_setting>

<digit-pl> <time_interval_unit-minute-pl>

<flight_id-not_creatable>

<flight_noun> of <digit-pl> <specific_aircraft_type-pl>

<flight_id-not_creatable-sing>

<flight_noun-sing> of <digit-pl> <specific_aircraft_type-pl>