non-stop backups

I realize previous days backups are consolidated, but when you look at the present days backups there are many for the same times. the seconds are different, but if it backs up every 5 minutes, how come there is a snap shot for 8:42:25, 8:42:36, 8:42:49, etc.. if i needed to restore from an earlier time that day which one would you pick, or do you need all from that time slot? seems very confusing yet previous days have only one. i'm using 2011

thanks
bob