In Resgrid the staffing level is the current state/staffing of a user. The default staffing levels are Available, Unavailable, Delayed, Committed and On Shift. Staffing levels are used to denote the users current working state or their current ability to respond to calls, dispatches, messages or work assignments. So "Available" would denote a normal response time, but if the person is at work that allows them to respond to calls they may be "Delayed" but their time to reach the station/scene would be slower then normal.
Available
User is available and can respond as normal.
Unavailable
User is unavailable and cannot respond.
Delayed
User is delayed, they can respond but it will be slower then normal
Committed
User is committed and cannot respond
On Shift
User is currently On Shift
Departments can create their own Status and Staffing Levels to match their needs and terminology in the Department Menu->Custom Statuses page.