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