Update README.md

README.md

@@ -15,7 +15,7 @@ metrics:
 ---
 
 # TL;DR
-Prometheus is an alternative of GPT-4 evaluation when doing fine-grained evaluation of a LLM & a Reward model for Reinforcement Learning from Human Feedback (RLHF).
+Prometheus is an alternative of GPT-4 evaluation when doing fine-grained evaluation of an underlying LLM & a Reward model for Reinforcement Learning from Human Feedback (RLHF).
 ![plot](./finegrained_eval.JPG)