While debugging some PCI issues in my computer, I came across PCI BAR assignment errors for BARs 13,14,15, and 7. My understanding was that there are only 6 BARs in the PCI specification, numbered 0 through 5. These are reduced to only 3 when using 64-bit BARS. There is also a ROM BAR, numbered 6.
So my question is: what are these BARs with higher numbers? I don't understand how they fit in with the PCI specification.