Driver A started as a part-timer a few months before Driver B started as a part-timer. Driver A worked 3 years and 4 months as a pre-loader then went full-time driving in 2005 and was given 1 year of full-time credit for his years as a pre-loader. Driver B worked as a pre-loader for 3 years and 1 month then went full-time driving in 2006 but he recieved two years of full-time credit for his part-time work. So when they bid vacations the lower seniority Driver B currently is getting one more week of vacation time than the higher senority Driver A. Can someone explain this to me?