Add scenario episode structure details

README.md

@@ -166,6 +166,8 @@ Hand-picked and categorized episodes that isolate specific game events — sourc
 | racer | 5 | 140 | 6 MB |
 | snake | 5 | 160 | 11 MB |
 
+Each episode contains 32 history frames + 1 pre-event frame, followed by up to 20 rollout frames (including the event). Rollouts are truncated early on termination.
+
 Each game includes a `same_state_different_actions` scenario that tests action-conditioning by replaying the same initial state with varied actions.
 
 ### Downloading scenarios