According to the Hawaiian Moon calendar 'ebb' will return with the 4 nights at the end of the month, which I have interpreted (cfr at hupee) as reflecting the idea of next month making itself 'felt' 4 nights before the old month ends:

1 Hilo 7 Ole-ku-kahi 14 Akua 21 Ole-ku-kahi 26 Kane
2 Hoaka 8 Ole-ku-lua 15 Hoku 22 Ole-ku-lua 27 Lono
3 Ku-kahi 9 Ole-ku-kolu 16 Mahea-lani 23 Ole-pau 28 Mauli
4 Ku-lua 10 Ole-pau 17 Kulu 24 Kaloa-ku-kahi 29 Muku
5 Ku-kolu 11 Huna 18 Laau-ku-kahi 25 Kaloa-ku-lua
6 Ku-pau 12 Mohalu 19 Laau-ku-lua
  13 Hua 20 Laau-pau

Tane (Kane) seems to begin his work with rasing the sky roof 4 nights before the new Moon light will enter. This could be an imaginative explanation of why Waning Moon arrives after 16 nights and not after 20 (the sum of fingers and toes).

When counting the path of the year 4 days are instead needed to add at the end, because 18 * 20 = 360 is not enough to cover 13 months with Moon visible (28 nights in each month). Sun and Moon are opposites, and therefore these 4 days should rather be added at the end than at the beginning.