Handwriting recognition with SVM, changing training and testing values

http://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_ml/py_svm/py_svm_opencv/py_svm_opencv.html In this example OpenCV gives, the training set is of 250 and testing amount is also the same. However when the testing and training numbers are changed, the accuracy goes down to 0. # First half is trainData, remaining is testData train_cells = [ i[:40] for i in cells ] test_cells = [ i[40:] for i in cells] x = 200 responses = np.float32(np.repeat(np.arange(10),x)[:,np.newaxis]) I have changed the values in above lines of code. What am I doing wrong? And what should x be?