What are "[]8" shaped side vias"?

[ryanwhite-stemcell]

In the layout checklist, what does "[]8" mean? I'm having trouble picturing it!

[azonenberg]

See figure 2-1 on page 25 of https://docs.xilinx.com/v/u/en-US/ug483_7Series_PCB. I'm talking about option C.

If you can figure out a better way to describe this in text (or want to contribute a license-compatible sketch of the layout) I'm all ears. Ascii art was the only thing that came to mind initially.