Using common sense, you scrolled down past #1 and clicked in reactions, where #2 is clearly visible, so only one can deduce that you clearly clicked reactions from #1.
I suppose my screenshot wasn't a good way of saying "as designed" to the OP, but if it's bothersome, they can ask for styling customizations and I'm sure they can get #1 to say "OP" (or less confusing wording for them).
But I understood it if that was directed towards me.
Shouldn't it just be "Members who reacted to message"? or maybe even just "Reactions" - the #1 doesn't seen to have any significance as it appeared to be exactly the same in multiple different threads I looked at. I assumed it was a bit of code that had escaped.
No need to feel stupid at all, I can understand how it could be confusing.
It's pretty much officially known as the "number" sign but it sure does have a lot of uses, and often the usage changes depending on context. Often when it prefixes a number, even in the USA who heavily refer to it as the "pound sign", it means number.
If you think about it, it must be one of the most flexible symbols in use, Pound, number, hash tag, people often use it as the sharp musical symbol (even though there's a different symbol for that). Crazy really.