The tk is wrong, the combo shouldn't have that at the start. For that combo you need to do the j.2c very close to the ground, which is what the tk is trying to say, but it's wrong.
The beginning of that combo takes a bit of practice to get down. You can practice the full combo by doing the j.2c on the way down from a jump, but the combo is usually landed by doing it at the start of a jump, and doing it early enough so that you can do the rest of the combo reliably takes practice.
tk means to do a motion, then jump, then press a button to get a special attack to come out in the air close to the ground. For example with Akiha do 2369+a/b. If you time it right you'll get a flame just off the ground. With this particular move you'd want to do 2368+a/b most of the time so you jump straight up instead of forward, but for most moves it doesn't matter. Theoretically you can do this with almost any air special, but it is easiest with 236 and 214 motions as you just need to continue the motion to 9 or 7 and slightly delay the button press.