Obviously there remains more work to do, as the Easter Islanders might have had ideas about different lengths of the week in winter and summer.

And if so, then it is quite possible that the (presumed) week in Keiti only covers the summer part of the year.

Though there is another possibility: that this week instead covers only the winter part. That would explain my difficulties with this pattern:

In the middle of the week there is less light than in the beginning and the end.

However, it might also be a picture of 7 periods of winter. E.g. with 26 days in each period (week?), 7 * 26 = 182 = 14 * 13.