Yes, you will need 20 volume (6%) developer (peroxide) to mix that with. You will probably also need or should use a "base" colour, something neutral like 6.0 Dark Blonde, or 7.0 Blonde, depending how fair you want the result to be, and you can mix the 2 colours in a 3/4 to 1/4 ratio.
So if you used 3 teaspoons of 9.23 and 1 teaspoon of 7.0, you would need to mix it with 6 teaspoons of 20 Volume Peroxide (6% peroxide). This would yield 50ml in all. So if you were doing a whole head, you would double all those amounts to make 100ml. Generally speaking that would do - a box dye from the chemist is usually around 120ml - but if you had long thick hair and were doing the whole lot, you might treble it to make 150ml which ought to cover most heads of hair. Remember, you can always mix up more dye as you go like the hairdressers do.
20 volume peroxide is what you need to "open up" grey hair, so you should get perfect grey coverage from that. Do a strand test.