In the attached post:
In-sample size is 4 (yearly October Data 2009-2012 - before first halving).
Out of sample size is 7 (yearly October Data 2013-2019 ).

This model was only deemed to show that with only 4 data you already get the stock to flow dynamics and you can correctly predict 2019 prices using only 2009-2012 data!

It is a different model from the full model that took in account I believe 111 monthly data points between 2009 and 2019 (r2 is also different).