Offers can be negotiated with the MIB. Their first offer is not their final offer unless they make a “formal award”.
The MIB (unlike a regular third party) can take as long as they like to respond to an offer or to accept an offer.
If the MIB make a “formal award” and it is not a reasonable offer, a client has to appeal to the MIB; the MIB can either grant the appeal and make a higher offer or submit the matter to an arbitrator for a final decision.
The arbitration process is effectively a paper-based hearing and should be treated as a small trial.