Face recognition - Sface match result evaluation

Thank you berak.
Indeed, my wording ref. accuracy is not correct.
Let me rephrase : “Let’s say the match method returns a cosine score = 0.300, what is the face similarity : 95, 90, 80… %”
I guess without the ROC (TPR / FPR), it will be not possible to extrapolate.
Any clue about next step ?
Thanks