Anapanasathi 16

The four Sathipathanas are ;
mindfulness of the bidy (kayanupassanasathipathana)
mindfulness of the feelings (vedhananupassanasathipathana)
mindfulness of the mind (Cittanupassanasathipathana)
and mindfulness of the Dhammas (dhammanupassanasathipathana)
in the first of the four, (kayanupassana), the practice is split into 6 levels, the first being Anapanasathi
Anapanasathi has 16 stages
The sixteen stages of Anapanasathi actually, when properly practiced also complete the full four stages of all four sathipathanas. For this reason i dont think it is necessary to study so much and theorize, all we need to do is practice the focus on the breath and pass through the 16 stages of Anapanasathi
14 is Kayanupassana
5-8 is Vedhananupassana
9-12 is Citanupassana
and 13 - 16 is Dhammanupassana
any comments?