The 3 viri glyphs in P are arranged close together in a pattern which suggests a final and 4th member of the group, viz. a glyph (Pb9-33) which I will call te pito (the navel) - earlier mentioned in connection with hakaturou:

 

Pb9-21 is different (drawn thicker) than the other two. We will take that as a sign of priority, and counting will therefore be done from Pb9-21 (in spite of the 9-29 in Pb9-29).

With Pb9-21 as number 1 te pito will be number 13, possibly an allusion to 13 * 28 = 364.