the answer is simple. bitcoin price fell. hence, the earlier buyers were able to fetch a better price for their bitcoins than the later buyers. so when balancing was done, additional shares were given to them. but this is the part i do not understand. in the first place, if every order was treated independently, and each one had just enough "bitcoin worth of money" to buy a neptune, how did the balancing resulted in the earlier buyers getting 90 additional shares for free?