If the end of a cycle is illustrated by the glyphs as a 'break' in day number 314 (counted from a presumed winter solstice day), then we should try to count backwards from Hb3-6 (where also the numbers seem to allude to a break) in order to find a beginning of the cycle, 3 * 314 = 942 glyphs earlier:

Hb3-4	Hb3-5	Hb3-6
64 + 250 = 314

With Hb3-6 as day number 64 + 750 / 3 = 314, we can count 3 * 314 = 942. On side b Hb3-6 is glyph number 105. If we subtract 105 from 942 there will remain 837 glyphs, a number greater than 648, the number of glyphs on side a:

837 - 648 = 189. Counting backwards from line Hb12 we have 51 + 53 + 67 + 65 = 236(!), and 236 - 189 = 47, i.e. Hb9-47 is our glyph:

Glyph numbers and days below are counted from Ha1-4.
Hb9-42	Hb9-43	Hb9-44	Hb9-45	Hb9-46	Hb9-47 (1104)
367			1104 / 3 = 368

We have arrived to the end of Thursday. The cycle of the H text is ending here (at least according to this reading). In order to get the numbers right we must, though, add 192 glyphs (64 days):

Glyph numbers and days below are counted from Hb9-48.
Hb9-42	Hb9-43	Hb9-44	Hb9-45	Hb9-46	Hb9-47 (1296)
367 + 64 = 431			1296 / 3 = 432