I believe you are supposed to leave it submerged until it sinks, they you know it has taken up enough water to germinate. I don't do it this way though, just the paper towel method with some Hydrogen peroxide.
just leave it cup if they float or sink does not mean there good i have done 100s of seeds like this some have floated 6 days and then sank and cracked leave in water til u get a tail about 1/2 inch long
sink, float, it does not matter whatsoever. i know this because i have grown dozens of seeds that have both sunk and floated and i couldn't tell any difference. they all sprouted, grew, and got smoked (or are currently flowering).
Ya most seeds float at first then once they sink it just means they have absorbed enough water to start germination, leave em in for a bit till you see a tail then into soil