Everyone is a little different. Some athletes do have a higher anaerobic capacity, fast twitch muscles and etc. so they can do the higher amounts. The two most important things are that you are going full gas! These are race intensity intervals so you want to be giving it your all like in a race. Secondly you do want to make sure you are staying over 130% of your FTP. This is zone 6 and anaerobic power. Have to stay over this to get the most out of the effort and training the system they are meant to train.
There’s a few different Tabata workouts we use, some with 20/10 work to rest intervals (like in the original Tabata protocol) as well as a couple of other configurations, like the 40/20s others are mentioning.
I’ve found with Tabata intervals, you don’t need to worry a ton about hitting an exact number but you do need to be ok with shutting it down if you don’t have the legs.
Tabatas are MAX intensity efforts. There’s no holding back. This kind of effort is short and intense which means you’re a lot better off going by feel than staring at your screen. If you crash and burn after 6 or 7, that’s fine, just stop there (at least, that’s what Izumi Tabata perscribed for his athletes, this plan may vary). If you’re not getting into zone6/ 7, you’re not getting the stimulus you need for this to be effective.
My personal favorite way to do Tabatas is with music made for Tabata intervals. Do a search for it and you’ll find a bunch of tracks. Typically there’s very quiet music during rest then really loud for the “on” portion. I like it because it allows me to just focus 100% on going all out. No looking at screens, no thinking, just give it everything when the music starts until it stops.