52840 USB DFU

When using nrfutil to upgrade the app for 52840dongle, you can see the data shown in the figure through the USB analyzer. The highlighted one does not quite understand the meaning. A total of 69 bytes.
I would like to ask the specific meaning, what should we send here if we make the tool for upgrading the application ourselves?
And why is there a suffix of 0xC0 at the end of each piece of data? Not in the official documentation.