The instructions of the sutta are as follows:
"It is like this, bhikkhus: the practitioner goes into the forest or to the foot of a tree, or to any deserted place, sits stably in the lotus position, holding his or her body quite straight, and practices like this: ‘Breathing in, I know I am breathing in. Breathing out, I know I am breathing out.’
1. ‘Breathing in a long breath, I know I am breathing in a long breath. Breathing out a long breath, I know I am breathing out a long breath.
2. ‘Breathing in a short breath, I know I am breathing in a short breath. Breathing out a short breath, I know I am breathing out a short breath.
3. ‘Breathing in, I am aware of my whole body. Breathing out, I am aware of my whole body.’ He or she practices like this.
4. ‘Breathing in, I calm my whole body. Breathing out, I calm my whole body.’ He or she practices like this.
5. ‘Breathing in, I feel joyful. Breathing out, I feel joyful.’ He or she practices like this.
6. ‘Breathing in, I feel happy. Breathing out, I feel happy.’ He or she practices like this.
7. ‘Breathing in, I am aware of my mental formations. Breathing out, I am aware of my mental formations.’ He or she practices like this.
8. ‘Breathing in, I calm my mental formations. Breathing out, I calm my mental formations.’ He or she practices like this.
9. ‘Breathing in, I am aware of my mind. Breathing out, I am aware of my mind.’ He or she practices like this.
10. ‘Breathing in, I make my mind happy. Breathing out, I make my mind happy.’ He or she practices like this.
11. ‘Breathing in, I concentrate my mind. Breathing out, I concentrate my mind.’ He or she practices like this.
12. ‘Breathing in, I liberate my mind. Breathing out, I liberate my mind.’ He or she practices like this.
13. ‘Breathing in, I observe the impermanent nature of all dharmas. Breathing out, I observe the impermanent nature of all dharmas.’ He or she practices like this.
14. ‘Breathing in, I observe the disappearance of desire. Breathing out, I observe the disappearance of desire.’ He or she practices like this.
15. ‘Breathing in, I observe the no-birth, no-death nature of all phenomena. Breathing out, I observe the no-birth, no-death nature of all phenomena.’ He or she practices like this.
16. ‘Breathing in, I observe letting go. Breathing out, I observe letting go.’ He or she practices like this."
This is all well and good but I don't understand how you follow these instructions. Are you supposed to go through the first four instructions in one sitting? or are you supposed to contemplate one per sitting or do you recite each instruction once in your head before moving on?