[kurumo]

That is simply incorrect. A GM can perhaps give a strong amateur (2000+) 1 to 5 time odds, maybe 1 to 7, in under a minute time controls. Larger odds would be arrogant, foolish or even suicidal, depending on the specific GM (rating, opening repertoire, etc.)

[RoboTeddy]

By amateur I was imagining ~1500. If in chess circles "amateur" means "anyone other than a master/grandmaster", then my statement as written is probably false!