I think it will look like this:

For example: 5000 ETH with 20 000 whitelisted participants.

  a.First 12 hours: max contribution x ETH, where x = 5000/4/20 000 = 0,0625 ETH

  b.next 8 hours: max contribution 2x ETH

  c.next 4 hours: max contribution 4x ETH

  d.next 2 hours: max contribution 8x ETH

  e.next 1 hours: max contribution 16x ETH