If you are in middle of davening shmoneh esrei during maariv and you hear the Chazan counting sefirah (or others for that matter) does it mean that since you already heard that night’s number you may no longer count [with a bracha]?
According to most poskim it is not an issue, and you may still count with a bracha, because you didn’t have mind to be yotza with his counting, and the person counting also didn’t have you in mind.
This idea is brought in Shulchan Aruch Horav 489-12, however it is a very novel idea, and is not brought in the other poskim. Especially since sefira is one of the mitzvos that we should specifically do on our own. See Piskei Teshuvos 489-8.