HCLr.fst and final.mdl decode a wav file dynamicly is none !!!

i have two question ,the first :
when i use "vosk-api-master/training/local/chain/run_tdnn.sh" train a model ,the model size is about 20M but the release model size is 70M ([vosk-model-en-us-0.22-lgraph](https://alphacephei.com/vosk/models/vosk-model-en-us-0.22-lgraph.zip) ,can u tell me why?

the second : when i use my 20M model ,i decode a file in final.mdl and HCLG.fst ,the output is normal ; but when i utils/mkgraph_lookahead.sh generate the HCLr.fst ,i decode a file by final and HCLr.st in a dynamicly way by language model,the output is none , can you tell me why?