The quantity of Gas delivered in the Delivery Month in which any NDDQ [Non-Delivered Daily Quantity] arose, and corresponds to the sum of NDDQs during such Delivery Month, shall be priced at the Gas Price for such Delivery Month reduced by a discount of:
(a) eight per cent (8%), if such Delivery Month falls on the months of October through March; or
(b) four per cent (4%), if such Delivery Month falls on the months of April through September,

provided, however, that if in any Delivery Month NDDQs arose on fifteen (15) Delivery Days or more, the quantity of Gas delivered in the Delivery Month in which the NDDQs arose, and corresponds to the sum of the NDDQs in such Delivery Month, shall be priced at the Gas Price for such Delivery Month reduced by a discount of ...

не понимаю, что значит on (!) fifteen (15) Delivery Days or more

при условии, однако, что если в каком-либо Месяце Поставки имеет место (возникнет) НПСО (Недопоставленный Суточный Объем) в течение 15 (пятнадцати) Дней Поставки или более...?