My card is slightly curved, will this affect the scoring result?

This is possible and will depend in particular on whether the curvature is natural or not and on the intensity of the curvature. A minor deviation in flatness formed naturally will have no effect, whereas a slightly more pronounced curvature or one resulting a priori from handling, will be likely to cause its surface sub-grade to fall. On the other hand, excessive curvature or torsion will lead to a refusal of grading in order to avoid an unsightly final result in our case.