If you did not receive the initial airdrop and have been waiting for Hardfork 24 to correct your balances, you were probably surprised to notice that a portion of the tokens remained undelivered. Liquid funds in the form of HIVE and HBD were corrected, but the function that restored the funds didn't properly take into account the tokens that were powered up and VESTS were omitted in the distribution round.
You can view the hardfork code here: https://gitlab.syncad.com/hive/hive/-/blob/master/libraries/chain/database.cpp#L2031
The accounts who have been waiting on the error correction have been incredibly patient through a frustrating period, and completing the airdrop as quickly and as safely as possible without another hardfork is a top priority.
Witnesses and developers have spent time since HF24 activation discussing all of the plausible solutions. There are two main ways to solve this, which would be to either have another hardfork to correct the balances, or to make a proposal. Since these funds are being held in the DHF, we could convert the received HBD to HIVE and power up the remaining outstanding tokens to the impacted users.
The advantage of doing another hardfork would be that the balances will be restored instantly and trustlessly. However, there are a number of issues that don't make this a good choice: it's very expensive in terms of developer hours, it involves creating, reviewing, and testing more code (testnets etc), synching the witnesses for deployment...and most importantly, it requires additional downtime for exchanges. All in all, it would take far too long for these users to have their funds corrected this way.
By making a proposal, we can ask for the remaining funds held in trust easily, without any code changes at all. There are a few downsides to solving this with a proposal: it may not reach payout for funding, and the outstanding VESTS will require roughly 117k HBD to cover, which means it will take about a month of payouts to gather. To manage the security of the large amount of funds in a transparent way, there would be a need to create a custodial multisig account. There is also the risk of fluctuations to the HIVE and HBD price that may result in the 117k not being enough. All of this would take extra time and coordination that would continue to impact these users.
After some debating, 
There is a wide margin included in this proposal to take price fluctuations of HBD into account. Once the proposal is approved,
@Howo has created the distribution script and encourages you to review it: https://github.com/drov0/restore-hf23-balances. If you are an impacted user, you may have gotten a test memo while preparation for this has been going on. This proposal truly is the best of both worlds for correction. It recognizes the importance of an immediate solution for these users with no security impacts on the ecosystem at large, but for it to happen we do need to support this proposal and
The 4750 HBD amount was calculated using the daily budget, which is the amount distributed daily to funded proposals. It was very important to make sure that no currently funded proposals would be be bumped out by this one, but also to pay 
