1. Perhaps the bulge means that this type of glyph is a compound, i.e. a mixture of two (or more) types of glyphs. If one of these is the simple eggshaped oval, then the bulge might represent this type of glyph:

Though mostly this type of glyph has a more pronounced middle part.

2. The fact that the bulge can be oriented in different directions might mean that the oval is like an orbit (in space or time - same thing) and that consequently the bulge may be like a pointer on a dial-plate. At first (periods 2-3) we have the bulge at the left and later at the top. But then the calendar must show only part of the month, because we cannot see the bulge at the right or at the bottom.

3. If I have guessed correct, then the type of glyph looking like a backwards oriented 3 could in itself indicate a position in time-space. We have seen this type of glyph twice before in the (presumed) calendar of the year. There they are located in periods nos. 18 and 30. But in both cases oriented exactly the same. Furthermore I have not seen anywhere any other orientation of this type of glyph. That 'proves' the orientation of the 'backward 3' does not express position in time-space. Could the meaning instead be something like 'emerging'?

4. I remember having read sometime somewhere about the Greek letter omega; that it is a picture of an egg waiting to hatch: W. And after hatching it is written: w.