What does “Awaiting release from previous registrar” transfer status mean?
This status means that there are no issues at this time, the transfer is being processed in a regular way and no further actions are required from your side.
According to ICANN's 'Policy on Transfer of Registrations between Registrars', the losing Registrar has 5 days to automatically release the domain after the transfer is approved via email. You might want to contact them and specifically instruct to release the domain earlier. However, in most cases this is a highly automated process, so there are no special actions required at this stage of transfer.