I think there's a good chance that what you are calling "chaff" may be seeds. Personally, I'd just plant them all and see what comes up. Have a look at this link, and the top left pic of seeds resembling yours. The writer does mention the various shapes and sizes are common in the same batch. Some other interesting info there that may help you in propagation.

I've always found Euc. seeds very easy to propagate, but YMMV...

Growing Eucs from Seeds

ETA...I don't consider your seeds to be tiny at all! I've grown many Eucs from seeds no bigger than dust.

I will defer to shax's expertise but in my limited experience, Euc seeds are in a hard ball or "nut" packed in with cotton like hairs. The non-seed is either going to be hair like fragments - obviously not what you are dealing with - or the hard capsule, the segments of which would retain a circular or ovoid shape and be hard as a rock. That's not what I'm seeing in your pictures.

Hi, David. As you probably know, Eucs have a wide, weird and wonderful assortment of capsules/pods/nuts. As do the seeds contained within...

I started doubting because received 11 pcs. of E. pulverulenta instead of 20 as paid for.

I'm a bit late to this but for what it's worth, the Eucalyptus seeds do look like seeds to me, not chaff.

It looks very nice.