The timer waits for a specified time; then it returns from sleep and resumes an AssemblyLine, that is, it starts a new cycle. You can use this Connector runs in Iterator mode only.
On attribute mapping, there is one attribute you can map into the work entry: a timestamp, which is of type java.util.Date. It will contain the time when it started the cycle.
Using Delta functionality with this Connector does probably not make much sense.