There is an affinity between this glyph and the six in the dark five+ nights (in 1a):

The 6th glyph does not look fully grown, probably it represents the extra night appearing only each 4th year. The four at the beginning might mean the 'Bacabs'. That leaves us with the 5th and it has these 'qualifying glyphs'

I believe this means the 'break' (that is a fact that we can see) between the years, a point of turning (bent backs), and the old year (left) 'handing over' (outwards hand) the 'rule' (open henua in the arm) of the right 'person' (new year).

And the outstretched 'leg' in the 5th and 6th glyphs represent the same thing. 3 times out of 4 the 5th glyph and 1 time out of 4 the 6th glyph represent the newborn year. The short left (seen from us) wing in the 6th glyph corresponds to the short right wing in the 5th glyph.

The outstretched 'handing over' hand (in the left of the two glyphs above) has via the right hand-like shape in the right of the two glyphs above - the new year - transformed itself into an outstreched 'leg' (in the 5th and 6th glyphs). Now we can see that clearly. Also we remember the hypothesis about this outstreched 'leg' being a sign of beginning. It is affirmed here.