[*] It's also worth noting that there are 2 categories for TAS timing: Humanly possible vs TAS-only. The former meaning that it's possible in theory for a human to achieve under "normal" conditions, the latter implying the opposite e.g. using left + right inputs at the same time which is not possible on a normal NES pad. The TAS in question was the current theoretical limit for humans.
http://tasvideos.org/Game/nes-super-mario-bros.html
[*] It's also worth noting that there are 2 categories for TAS timing: Humanly possible vs TAS-only. The former meaning that it's possible in theory for a human to achieve under "normal" conditions, the latter implying the opposite e.g. using left + right inputs at the same time which is not possible on a normal NES pad. The TAS in question was the current theoretical limit for humans.