PI means the owner reported that the dog has permanent identification (microchip, tattoo).
VPI means the ID was verified by the veterinarian, tech, etc.. that collected the blood.
Remember to check LabraData as well. There are about 200 dogs reported in OFA and about 80 in LabraData. Some of these are the same dogs, but some are not. A higher number of the LabraData dogs are reported as carriers. I suspect this is because reporting was free and it would cost $15 to report a carrier to OFA LabraData also accepts reports from the research phase of EIC testing. Some owners have opted not to have those dogs retested to get the "official" report, so those results will never be submitted to OFA. Just remember to look both places to get the most complete information.