Calculate operative times by using time measurement techniques

I have a raw time log from last week's site sessions with start and stop timestamps and a separate sheet of activity codes. Calculate operative times for each activity per technician, then produce a single column of total operative minutes per technician for Friday's review. Check for overlapping intervals and for any gaps larger than 15 minutes that look like missing stops before you finalize.

Before I hand this to the project leads, make the operative-time output easy to trust: surface each technician's total operative minutes at the top, show the three largest activity blocks and flag any day with overlapping timestamps or gaps over 15 minutes, and make the calculation transparent by adding one-row notes that show which rows were excluded and why.

I merged start/stop timestamps and summed operative minutes per technician, and now two technicians show totals larger than their rostered shift. I suspect overlapping intervals or duplicated entries from device syncing, but I don't know which days or which entries to treat as duplicates without losing legitimate work. What is the most likely cause and the safest next step to resolve it before reporting totals to operations?

Across several projects we keep finding overlapping intervals and then hand-editing the spreadsheet, which eats time and makes audits harder. Recommend one habit change and a small enforcement rule that will reduce rework and preserve an audit trail, so we stop fixing the same timestamp errors every week.