Update README.md

Looks good overall!

Added a short description of some tree states

README.md

@@ -262,7 +262,8 @@ The oasst_ready-trees file is normally sufficient for supervised fine-tuning (SF
 2023-04-12_oasst_all.trees.jsonl.gz         66497 trees with 161443 total messages
 2023-04-12_oasst_all.messages.jsonl.gz     161443 messages
 ```
-All trees including those in states `prompt_lottery_waiting`, `aborted_low_grade`, `halted_by_moderator`.
+All trees including those in states `prompt_lottery_waiting` (trees that consist of only one message, namely the inital prompt),
+`aborted_low_grade` (trees that stopped growing because the messages had low quality), and `halted_by_moderator`.
 
 
 ### Supplemental Exports: Spam & Prompts