This type of glyph is in principle graphically constructed out of pieces of wood (four in this instance). The glyph
does not only stand for a period of time, but also (and primarily?) for wood. Exactly like this the Mayans too regarded time periods as connected with trees, as I have read in a book (Coe):
"...one sign, very common in the codices where it appears affixed to the main signs, can be read as te, or che, 'tree' or 'wood', and as a numerical classificer in counts of periods of time, such as years, months, or days."
I suggest that this glyph (see top) shows a kind of 'tree'. The trees were extremely scarce on Easter Island and you would not expect the few trees there were to be straight and stately. Thursday is the day of Jupiter and he is causing thunder and lightning. Often old oaks are struck, one of the reasons for showing trees in Thursday.