You won 300 DC digital cards. The DC digital cards have no nominal value if unsold.
Donatello Club digital cards are issued by Donatello Card Limited and are also used as marketing tool and units for contest rewards.
I suggest that you give them away to your friends or sell them online as a verified user at https://Donatelloclub.eu.
When you collect 1000 DC digital cards and you really want to get rid of them then @Donwhale can buy them from you for 3USD.
Please also read, https://donatelloclub.eu/upgrade-your-account.