Why does ST03n appear to give conflicting stats?

Ok, so I'm looking at the month of May in ST03n

Workload Overview for the month says:

• average % DB time is 61.6%,
• average % Roll wait time is 14.1%

If I look at Time Profile and work out the averages manually for the same month

• average % DB time is 57.92%
• average % Roll wait time is 16.91%

More of a rhetorical question really but why does different areas of ST03n report the same thing differently?

Which is accurate? Which is correct?