Catalan Zodiac Rose S.XV

[MarcoP]

What I don’t understand is why, if a lunar cycle lasts 29 days, they used only 19 tables.

It appears to be a pseudo-astrological divination system (similar to some kinds on geomancy, where you draw a fake astrological diagram/horoscope). I don't understand the details, but it seems that you need to select a location on your hand based on fig.XXV.

19 locations are marked on the hand:
1 nail+2 phalanxes for the thumb, (1 nail+3 phalanges) *4 fingers = 19