Five is a number connected firstly with the five fingers, the pentagonal form of Venus stations in the sky, and the extracalendrical five nights between one calenderyear and another, the nights when gods are born.

My idea now is that those last five nights, located diametrically opposite to summer solstice, give reason to signify the period between summer solstice and winter solstice (whereas number 6 then refers to the first half of the year). The train of thoughts leading up to this idea started with two observations:

1) There are markers indicating 6 + 5 = 11 among the rongorongo glyphs, e.g. (Gb2-6):

2) The presumed yearly calendar of Small Santiago has a pattern for markers with the numbers 4, 5 and 6, where no bunch of six markers appear in the second half of the calendar.