The pie symbol indicates that the element is being uploaded or downloaded to/from icloud servers.
The grayed part of the pie represents the percentage of data already transmitted so in your case as this part is very narrow it means that for each file the update has just started.
The pie symbol indicates a manipulation of a file of some kind. As @LouisLac said, this could be upload/download from iCloud, but it could also be
- Transferring from a drive to another Drive
- Transferring from network drive
- Copying a file
- Safari (and other) downloads from the internet
- and many more....
Since you are taking about AFP (Apple Filing Protocol), you are most likely referring to either
- Transferring from internal to network
- Copying from network to network