From the hawaiian airlines mastercard website

[3] Companion Discount Benefits: New Primary Cardholders are eligible to earn a one-time 50% off discount toward one published roundtrip coach fare for a Companion. One-time 50% off discount is valid for 13 months from account open date. Allow up to 5 days after account approval for companion discount to be available for use. Upon payment of annual fee, the Primary Cardholder is also eligible to earn a one hundred dollar ($100) discount off one coach companion ticket on each credit card account anniversary, which is valid for 12 months from account anniversary. Discounts are valid only for coach fare for named HawaiianMiles member and their companion for roundtrip travel between North America and Hawaii booked directly through the Primary Cardholder’s HawaiianMiles account using his or her Hawaiian Airlines World Elite MasterCard and are subject to change. Named HawaiianMiles member and their companion must be booked on the same reservation, discount will be applied to the companion coach fare. Ticketing by E ticket only. Discount not applied to taxes, fees, and surcharges. Government taxes and fees and carrier-imposed fees will be applied to each ticket purchase. Other restrictions apply. Cost subject to change. Fares are subject to availability. Additional baggage charges may apply. Offer may not be combined with, applied to, or applied towards HawaiianMiles flight awards redeemed using miles. Offer not valid on Neighbor Island flights, multi-city reservations, codeshare flights with Hawaiian codeshare airlines, First Class or Extra Comfort fares, or open tickets. Discount cannot be applied to tickets already purchased. eCertificate offer can only be redeemed through HawaiianMiles’ member’s account on HawaiianAirlines.com. eCertificates are not transferable, have no cash value, and will not be replaced if lost or stolen. eCertificate may not be combined with, applied to, or used in conjunction with any other discount, promotional offer or tour package. eCertificate does not apply to vacation package bookings, including flights booked with a hotel on HawaiianAirlines.com. Flights booked in H and K class of service may not qualify for other airline frequent flyer miles. Standard Hawaiian Airlines eCertificate Terms and Conditions apply.