Contract Ticket

Does anybody know what the ticket contract numbers mean as indicated in column two of the Canadian passenger lists? Is there a way to trace the origin of the ticket via it's number? I'm hoping the number somehow indicates an agent or a grouping. My grandmother was on the S.S. Melita in May 1920 sailing from Liverpool to Quebec on ticket # E 3/780. I've run through the passenger list and there are about 20 other tickets numbered exactly the same, "E.3/688 to 806". Her friend had ticket number E 3/779, so they were probably purchased together. All of these people were domestics or laborers and all except two were Church of England. Those two were Baptists. The ticket holders were between the ages of 16 and 32. Other tickets have four or five digits and no letters or just one letter and some digits with no spaces or bars. We're trying to find out how and why my grandmother went to Canada.[:)][?]