Harold Camping's numerology: 7,000 years of creation history derived from combining Genesis 7:4 and 2 Peter 3:8

Camping was a young-earth creationist who believed he could calculate the date of creation from Scripture. His system: (1) Genesis 7:4 — God told Noah 'in seven more days I will cause rain.' Camping extrapolates: 7 symbolic days = 7,000 years of creation history. (2) 2 Peter 3:8 — 'With the Lord one day is as a thousand years' — supplies the conversion factor. Combined: 7 days × 1,000 years/day = 7,000 total years of history, including a future 1,000-year Millennium. Mike objects: Genesis 7:4 says '7 days' not '7,000 years'; why not 40 days (40,000 years) since it also rained for 40 days and 40 nights? The absence of rules allows any number to be used.