Multiple volume lines per track in Garageband

When I'm working on a midi arrangement in Garageband, I'm constantly making adjustments in Volume, Pan, Note Velocity, etc. for each track. By the time I'm finished with the arrangement, I may have as many as 5 yellow volume lines. I don't know how, why or when they keep popping up but I need to find out so I can stop it. I don't know which one is the current line so I have to adjust all 5 lines to the same levels to be sure the volume is consistent. I'm quite sure I'm doing this wrong and I'd love for someone to tell me how to keep it at one volume line. Thanks in advance!

baybob

[Edited by Moderator]