Tabata means 20 seconds of work, 10 seconds of rest. You’ll repeat all 6 rounds before moving to the next movement. You’re counting the number of reps you do each round. You can either write them down or just keep a running total for each movement in your head.
Many people can’t do double unders with a jump rope, that’s ok, some other options:
-single unders (IE traditional jumping rope)
Don’t Have a Jump Rope?
-“Box” jumps on a very short box