Normalised Correlation Value after applying DCT

Hello everyone

i am applying image normalization technique and DCT technique for embedding and extraction watermark image. here i am getting Normalized Correlation with negative sign after extracting watermark image. e.g.

   -0.9967
   -0.9966
   -0.9896
   -0.9697
   -0.9946

i just want to know that is it right or wrong ? why NC value is coming negative either due to applying DCT or image normalization ? plz clear my doubt.. thanks in advance