Mercury and Jupiter are prior, but - we should remember - at Ka1-1--2 they have been drawn intentionally 'invisible':

This means that Ka1-3 is the first glyph to count. We can compare with how it is practical to begin counting the nights of the month from the time the new moon becomes visible.

The 24 glyphs in line Ka1 should be reduced with those 2 at the beginning, and Venus will be both the beginning and the end of the 22-glyph long cycle:

Of course this can be due to pure chance, without any intention by the creator of the text. However, number 22 was in the mind of the creator, that we have discovered earlier (cfr the excursion at marama):