Hello Md Aminur Rahaman,
Welcome to Microsoft Q&A,
"Completed Work" in Azure DevOps is not designed to represent daily attendance or working hours. It's a running total that the assignee updates manually as they log effort against a task. It doesn't natively map to calendar days, doesn't reconcile against actual clock time, and depends entirely on whether individuals bother to update it. Using its sum as a proxy for attendance or daily utilization is a well-known anti-pattern, teams that try this usually get gamed numbers (people back-filling values to look consistent) rather than real signal.
The honest, doc-backed answer would be that it's meant for sprint capacity planning and burndown tracking, not HR-style attendance or utilization measurement, and Microsoft's own guidance on capacity planning treats it that way.
Please Upvote and accept the answer if it helps!