I estimated the number of glyphs in line Rb9 to be ca 30. But there are only 8 visible, and none of them in full:

...		...
	Rb9-101
...				...
	Rb9-201	Rb9-202	Rb9-203
...			...
	Rb9-301	Rb9-302
...			...
	Rb9-401	Rb9-402
Barthel has no description of line b9 - it was too badly damaged for delivering any information. Fischer has, though, a photo which shows that the glyphs Rb9-201--203 are located near the center of the line.

Definitely the odd line Rb9 as such is a sign, because we expect the tablet to have twice 8 = 16 glyph lines. I no longer think there once were twice 9 = 18 lines on the tablet, 16 is a much better number, we have learned.

Counting from the last glyph space among these 30 in line Rb9 the number of glyphs in the text maybe was intended to be 451. But if we take away 30 + 1 = 31 (the number of glyph spaces in line Rb9 + 1 more because we have counted the last one twice) the length of the text will be 420. 420 = 14 * 30 is a reasonable number, and we can therefore guess line Rb9 should not be counted, presumably because it represents winter solstice.