Please could you point out where in that paper it says so? I couldn't find what you claim is written in the paper: There is no mention of "hour" or "hours" anywhere in the paper, nor "days" associated with either "2" or "two" and "adapt" is only mentioned in the heading I quote below, the contents and two study references. This is a quote from the paper you cite:
Adaptation to ketosis
During starvation, ketone body levels increase from day 3 and continue to rise to reach a plateau around 8 mmol/L after 5—6 weeks of starvation.
which seems to back what we were saying. No?