Continue for five rounds. Return to your own pattern of breathing and relax completely. Then invite your exhalation to be twice as long. This means that if you inhaled to the count of three, you will try to extend your exhalation to the count of six. Experiment a little until you find a ratio that is comfortable for you.
Nothing is to be gained by a ratio that creates tension.
Should you feel dizzy, short of breath, or light-headed, simply return to your own way of breathing immediately and wait until the sensations subside. You have probably been trying too hard. Then resume the practice in a more relaxed manner. Continue for five rounds. Return to your own pattern of breathing and relax completely.