Cycle Time
Cycle time is how long the actual work on a task takes once it's started, from first touch to finished, excluding the time it spent waiting in a queue beforehand. If a support reply takes ten minutes to write but sat in the inbox for two days first, the cycle time is ten minutes while the lead time is two days and ten minutes. Cycle time measures the work itself; lead time measures the customer's whole wait.
For a lean founder the gap between the two is the insight. When cycle time is tiny but lead time is huge, your problem isn't speed of execution, it's everything sitting in queues, which usually means a capacity or prioritisation issue, not a skill one. Working harder on the task won't help; reducing the backlog or removing the wait will. Tracking cycle time also tells you how much real capacity a process consumes, which is what you need to know before you take on more clients or decide what to automate first.