Those plants are still too young and small to have produced seeds, they need to mature out of the water to bloom and set seed.
You've got a generous amount of seeds in that packet, 7500 pcs is a lot.
If you want to remove the seeds, your best bet is to gravel clean the substrate and hope you can vacuum them up.
Getting started with seeds: seeking advice
Re: Getting started with seeds: seeking advice
The plant resembles duckweed, but I'm also thinking it could be a type of hemianthus, possibly from Cuba. I'm really torn about the seeds, as it seems unlikely they'll work, but I've seen some people succeed with this. A lot of seeds sold aren't suitable for underwater life, which is why they often fail. However, I do know some people have made it work - I just don't know their methods.