I think you may want to look at accuracies
as in
> require(e1071)
> model <- svm(Species ~ ., data = iris, cross=5)
> model$accuracies
[1] 100.00000 96.66667 93.33333 96.66667 93.33333
I assume these are percentages for the accuracy of each fold. You could if you wanted then take the mean.