Problems using TVals parameters in perfcurve function

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Hi,
I’m failing to replicate the ROC curves produced by the “Classification Learner” app. My problem is a multiclass classification problem with 5 classes. My final goal is to optimize the choice of a specific classifier based on the false negative rate of a particular class (-2). Using KNNs as a first choice, I’m trying to replicate the ROC curve produced for positive class -2 in the app, but if fails as my ROC curve seems to have much less points than the one from the app.
I tried to set manually the thresholds using the TVals parameter of the perfcurve function, but cannot understand the size of the X, Y, T outputs of the function:
thres = 0:0.001:1;
[X,Y,T,AUC] = perfcurve(partitionedModel.Y,posClassPosteriors,-2, 'TVals',thres);
length(T)
ans=
10
Can anyone explain this to me?
Thank you very much in advance !

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