Apple - In activity monitor what time frame is the data sent / received data from?

For the top two figures, since last boot; for the bottom two, current.

After comments: It may be since launch of Activity Monitor - I have mine launch at boot & it stays open all the time, so I probably didn't notice the potential discrepancy.
The little graph is 'since switching to that tab', as it doesn't log more than about 5 minutes of data.

This machine's been up 9 days, this looks about right for my standard usage -

If I initiate a large download, the bottom figures become this [on a 150Mb/s line] -

The graph scale auto-zooms, so the earlier few KB/s vanishes into a flat line.

Once the file has finished downloading, the top figures show the increase of about 2GB & the bottom pair goes back to being relatively idle