Transfers are good for unlimited trips in any direction for at least one hour after issuance.
For transfers from local to transbay service, pay transbay fare on first bus and request transbay transfer, good for full fare on second bus. Transfers from transbay to local service are free. Your ferry ticket is actually a three-part ticket that includes free transfer stubs to AC Transit buses. You can ride free on AC Transit buses to and from the Jack London Square area or the Alameda ferry dock. DB Express passes and transfers accepted as local fare credit.