When setting up room resources and room lists in Exchange / Office 365 the default time slot size is 30 minutes, but sometimes you want a quick meeting that’s less than 30 minutes. Unfortunately, meetings less than 30 minutes are not bookable with the help of room lists. However, you can configure room resource time slots to accept 15 minutes in Outlook Web App (not supported in Outlook client) by following this guide.
Connect to Exchange PowerShell either locally on the server or online
To modify the work hours of a specific room resource in your organization use the following PowerShell command: