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"unique cards" - the total number of individual card types that you have. So if you had 3 "R1 Classic Punk" cards and 2 "E9 Debbie" cards then you would have 2 unique cards.

Hope that clears it up.

thanks @risingstargame does that also apply if you only had 1 card that was unique ie just one E9 Debbie to still qualify as unique or do you require at least 2 of the same to benefit?

Just one will count. It's the total unique cards you have of any number.