Grammar doesn't work with trained model

I had used mini_librispeech to train the model used in vosk, when i used the HCLr.fst to recognize the fixed text GRAM defined as "ONE TWO THREE FOUR ...", the recognition results of vosk is wrong; while i used the HCLG.fst ,the recognition results can be ok. I have no idea how to get the correct model of HCLr.fst. Looking forward to your reply！