Opencv3.1-Train dataset for temp stage can not be filled. Branch training terminated. Is this error if not how can i improve it further ?

edit

I used following command to train the cascade-

opencv_traincascade -data /home/ishan/ishan/opencv-haar/classifier -vec /home/ishan/ishan/opencv- haar/merged_vec/samples.vec -bg /home/ishan/ishan/opencv-haar/negatives.txt\ -numStages 10 -minHitRate 0.99 -maxFalseAlarmRate 0.5 -numPos 1350\ -numNeg 623 -w 20 -h 20 -mode ALL -precalcValBufSize 512\ -precalcIdxBufSize 512

After Stage7 it says: Train dataset for temp stage can not be filled. Branch training terminated.

I want to ask is it an error ? If yes how to rectify it and if not then how can i further train the model ?