A while back, we changed the default duration of unavailable and availability blocks to 30 minutes. We made that change because the default duration was not applied consistently. We received feedback that people were missing the old default for unavailable blocks, which was the duration of the practitioner's default appointment type. We've now made that the default for both unavailable and availability blocks.
If a practitioner does not have a default appointment type set, 30 minutes will be used instead.