Sorry if this issue has been posted before, but I couldn't find it

I am using Weka as a classifier, and it has worked great for me so far. However, in my last test, I got a 1.000 ROC area value (which, if i remember correctly, represents a perfect classification) without having 100% of accuracy, as can be seen in the Confusion Matrix in the Figure.


My question is: Am I interpreting the results incorrectly or am I getting wrong results (maybe the classifier I am using is badly programmed, although I don't think it's likely)?


I've tested it in versions 3.6 and 3.8 and had the same problem in both of them.

Thank you!