I have a trace, on Thread Time (with StartStopActivities), the method called HighCPUArraySort registered about 16 seconds (16471.5 inc) CPU time:

But on CPU stack, it shows only have about 8.5s (8515.0 inc) CPU time:

Why is it significantly smaller number on CPU view than it is on the activity view?

Trace session (etl) attached:
728d7e2465f04ab2992cb9177322507f.etl.zip

Can anyone help take a look? Thanks.