well wat i do wit my S3 and S4 is dat i use S3 on city as like downshift to get more power and S4 i use dat one da freeway. but tis is wat i use wit mine, i may b wrong or sumthing
is so you can "down shift" lets say going up hills or something... the numbers are the gear that you are in... you can down shift but you can't "up shift".