it means pull-off you just take your finger off the string and have the other finger on the 7th fret when you take it off the 9th and don't hit the string again
index finger on the 7th fret, ring finger on the 9th. pluck the note, and pull your finger off the string, leaving your index finger pressed down on the 7th. dont just take it off, you want to pull the string with your finger ever so slightly, so that the 7th fret note will sound clearly.
It's a secret communist code using top-secret Soviet Russian synmbols.
remember not to just lift your finger of the string cos you will not hear it. try to pull it off it you know what i mean.