A line chosen at random from n lines has a 1/n chance of being the slowest. Consequently, except when there is only one line, you are not "likely" to be in the slowest line. When there is only one line, the slowest line is also the fastest one. When there are 2 lines, you have even odds of having selected the slowest line. When there are several, you are just as unlikely to have selected the slowest one as you are to have selected the fastest one.
A line chosen at random from n lines has a 1/n chance of being the slowest. Consequently, except when there is only one line, you are not "likely" to be in the slowest line. When there is only one line, the slowest line is also the fastest one. When there are 2 lines, you have even odds of having selected the slowest line. When there are several, you are just as unlikely to have selected the slowest one as you are to have selected the fastest one.