Greek sigma letter for move in Lichess database

While playing a correspondence game:



The database for move #14 for Black has 2 moves with Sigma, rather than board moves.

Is this bug or does Sigma designate something?

sigma is the mathematical symbol for a sum. it's there in every position, not only the one you mentioned. it is always on the bottom of the list, and it shows the sum of all results for the current position, for all possible next moves. the position you linked was only played twice on lichess and both were wins for black.

Ah, ok. Thank you.