The next-to-final paragraph of the answer read:
-In a third scenario, the gastroenterologist admits the patient at 9 p.m. on Thursday and does not discharge the patient until 9 a.m. on Saturday. In this example, you may report one unit of 99218-99220 for Thursday, one unit of 99218-99220 for Friday, and the discharge (99217) on Saturday.-
The article should have stated that you should report one unit of 99211-99215 (Office or other outpatient visit for the evaluation and management of an established patient ...), not 99218-99220, for Thursday (keep in mind that the observation unit is technically an outpatient, not an inpatient, place of service).
You should only report one unit of 99218-99220 per observation stay because these codes are for initial care.