Multiple threads about it in the feedback forum...
https://hotcopper.com.au/threads/whats-the-symbol-mean.4058368/
https://hotcopper.com.au/threads/what-do-those-little-light-bulbs-mean-on-some-posters.4060588/
And a couple from admin
https://hotcopper.com.au/threads/great-analysis-update.4050763/
https://hotcopper.com.au/threads/great-analysis-not-to-be-confused.4035640/