I want to explain the logic behind 50% initial payments:

For each claim you have a certainty of its validity. You have the sum of funds from before the site had the database stolen which is equal to the site's previous balance. This sum must be distributed among claims somehow.

Ideally you would mark claims that you thought were accurate and those that weren't (based on what the data indicates to us). Then you would end up with some total value which you compare to the total funds available.

If less than the total funds, then be more permissive and allow certain more claims in. Repeat the above step.

If more than the total funds, then knock out low certainty claims and maybe redistribute funds among lower certainty claims (better that someone who is maybe legitimate, gets something rather than nothing).

You then end up with claims that are refunded with a best-fit according to the available data.

However people demand funds quickly. So as a compromise, we make 50% payouts initially (for claims we are highly certain are accurate). This allows an error margin so that in the final step we can still juggle balances around to resolve payments for everybody. The only downside is that you cannot decide to pay someone 0% after you've paid them 50%.

Then once people have been refunded for 50% and the final balances are decided, the process goes back over payees and refunds them for the remaining amount. I assume the final step should not take long given that it's just making payments out for known beneficiaries.