Some sink right away
Some will not ever sink, but they may grow.
Mine hardly ever sink. I add a little peroxide and the tiny bubbles keep them afloat.
Don’t pay any attention to the float sink advice. It isn’t 100% accurate
The few sinkers I ran across were duds. If it were me, I’d consider dropping one more to guarantee what you are after. Either you get what you want or you will have an extra. At least they’d be the same age.
I will take a clean spoon after a day or two and tap the floating seeds and they usually sink right to the bottom. Funny enough, one time I left seeds to soak and couldn’t get to them for a few days and I had a floater on top of water with a tail coming out of it. It was the only time I ever had that happen. Just my two cents. Good luck with your grow.