I am starting to use the NaiveBayes / Simple classifier to classify (Weka), however I have some problems that need to be understood when examining the data. The dataset I'm using is weather.nominal.arff.

While I am using the test use test from the parameters, the result of the classifier is:
Correctly Classified Instances 13 - 92.8571 %
Incorrectly Classified Instances 1 - 7.1429 %
a b classified as
9 0 a =yes
1 4 b = no
My first question is, what should I understand from the wrong secret instances? Why did you get such a problem? Which attribute collection is incorrectly classified? is there any way to figure this out?
Secondly, when I try to do 10x cross-validation, why do I get different (less) correctly classified instances?
Results:
Correctly Classified Instances 8 57.1429 %
Incorrectly Classified Instances 6 42.8571 %
a b <-- classified as
7 2 | a = yes
4 1 | b = no