Long seemingly defensive response for what was an innocent comment 
I have been experimenting and reading about Blynk literally (and in the correct literal sense) every. single. day. for almost a year and a half… and I still need to rtfm 
And I also have a bloody dented wall… can’t seem to remembery why 
That is the vPin you assigned to the Widget in your App project of the sending device… it is clearer in the example referred to from the documents (at the end of the Bridge doc).
In your searching did you find this?