I'm not sure of what those designations were meant for in your case, but the tail is used for "any relevant info" that the designer is trying to convey...ie could be a company's welding procedure that the designer wants them to use. I generally place the prequalified joint designation there so my guys can easily reference their welding manual for the correct procedure. I have the joint designation placed right beside the page number in the manual that I created for our company.
John Wright