Weird Numbers for amount of seeds

That happens when there's not enough room for one seed to be stored in the Storage Bin, so dupes split the seed into decimal values. Each part of the split seed can then be planted making it possible to multiply seeds as you get a full seed upon uprooting it.

This exploit can be used to make tons of Wheezewort seeds for minimal effort

I am having the same problem.

It's not a bug.

As Gnarmaw explain, it's due to the storage method, because the duplicants can pick up a fraction of a seed. And after that, this fraction can be planted and gives a plant without waiting for the rest of the 1 kg of seed.