There is Absolutely No Proof. . .

This particular glyph means "twenty" according to all the translations given of it. In one book,the writer had not found a single case where this symbol MUST mean the "moon."The writer further stated that there is no linguistic association between the word twenty "Vinal," or "kal," as it is translated in Yucatec, and Moon, "U" of Maya.

David Kelley, in his book, the Deciphering of the Maya Glyphs, discovered that this particular glyph is only associated with Bird Jaguar of Yaxchilan, as Ah Kal Chac or "Great Ruler." (p. 155, p. 223) He stated that kal, the complete moon glyph, might also refer to "king" in other texts. Otherwise, this glyph appears to relate to "imprison, enclose, and ruler."(p. 323) Nevertheless, there is a linguistic connection never mentioned. The Asian word for Moon,"Yüe," is similar in pronounciation to the Maya word "U." Since transoceanic travel has never been proven, this element is neither recognized nor acknowledged.

In Asia and Asia Minor, there are more than a few Moon dynasties. the Maurya of India, the Sassanian of Persia, Ghengis Khan's Ta Yüeh, Kamar(Moon) Rouge of Viet Nam, Egypt records (XIX Dynasty) as city Dapuna, i.e.,(Daphne or French Dauphine), Hebrew, the Hillel and finally in Europe as the Diana (Daphne)/Aphrodite/Venus culture of the night, commonly referred to as witchcraft. If there was a Maya connection with the Moon dynasties around the world, then Bird Jaguar also would have carried the "U" (Moon) designation.

Is there no reference in Maya that will connect this particular glyph to the Moon? In the Dresden, (Villacorte numbering system) there are eclipse tables.

Dresden Variants
D35, top and bottom registers.
D36, only in the bottom register.

D37 sitting on top of sky band and in the top register.
D38, it is in the text of the middle register together with a sun eclipse symbol.

Even D39 shows the kal under the sky band above an eclipse sign.
D40 it is in a sky band. Its presence within the sky band indicates that it is a heavenly body, whether a star, a planet, a comet, or an asteroid.

A Jupiter hook-eye-form appears on D45 in the middle register, and the kal is below in the sky band. Was the moon in the Jupiter constellation at the time of the event recorded here? Jupiter, is also called Akbal and part of the numbering system. So we have a Vinal (20) as the Moon and Akbal (3) as the planet Jupiter. The same concept as our Sunday, Monday, etc.
On D54, the kal is found in the upper register of the text while the kan is described in the lower.

D56 shows the kal glyph in the sky band over the kan sign. This glyph could give a twenty (20) count for the Moon, to indicate the 260-day cycle of 13 moon months. If this is true, then twenty is a viable number for this glyph also; but not ONLY.
Only one time does a Casper-like figure replace the kal glyph in an eclipse form. So we can assume that the Casper figure may be a more serious event that occurred with an eclipse. Sure enough the flaming bird beak form of a vulture is included in the text.(D57).

Page 58 shows the kal glyph, again within an eclipse glyph.
At the bottom of page 65, there are two eclipse glyphs. one encloses the sun glyph at its center and the other the kal glyph as the Moon.
The Madrid Codex has many references to the Moon as this glyph. However, in several places, the Moon glyph is split in half. Maya Cleft Moon This agrees with a a Persian illumination Persian Cleft Moon which shows the Moon with a bar down the middle of its face. (M91 and M93, both pages across the first row) Of course, there is no connection between the two; the Maya glyph was done in the Yucatan and the illumination was done in Persia. (See Persian Ideographs in Their Illuminated Manuscripts.)