So, for now from 90 units you sold one for 500 and a few for 67-69 ( they might want to buy all, but there's no guarantee)

That is exactly correct! It will be at least 1 and could be all 89 remaining (assuming no one outbids you).

What happens if you don't get enough buyers for all 90 units ?

Then round 1 is over with and we move to round 2 which is a sealed bid at 2x the highest bid from round 1. Currently that floor price would be $1,000.

I should also note that round 1 buyers have right of first sale in future rounds. Meaning if anyone buys now and wants to sell in a future round, theirs will sell before ours.

The point is to ensure that these find their proper price, so we take active steps to prevent the price from falling.