Max: Upstream rate = 66064 Kbps, Downstream rate = 345788 Kbps
Bearer: 0, Upstream rate = 49871 Kbps, Downstream rate = 330011 Kbps
303139 (BRAS) / 0.88 = 344,476 (rounded)
330011 (sync (modem)) * 0.88 = 290,410 (rounded)
313174 (sync (user portal)) * 0.88 = 275,593 (rounded)
313174 (sync (user portal)) / 0.88 = 355,880 (rounded)
I have a feeling it is closer to 91-92% as opposed to 88%, since the first two calculations seem to make sense using that. I actually don't know the answer, but I would not be too surprised if G.fast needed a larger overhead for high INP.