And I’ve seen a lot of kanji so far in my journey but I’m yet to encounter 〆, it looks so different!
According to my dictionary the word is the polite form of shimeru 〆る and means ‘to total’ or ‘to sum’
Yeah that was how I read it too, partially because of the 今日いっぱいで
It has a couple other meanings too, including shims being the ending thing for a drinking party, ending the party itself, or in the case of totaling it’s usually totaling after cutting off an end for the period. Like everything I can think of has some connection to there being an “end” though.
The only time I encountered this was when I was playing an MMO. One of my guild mates would create a party for 20 (for a dungeon raid), and once 20 players applied, that symbol would be used to indicate that you would no longer be able to apply to join the party.