Why was the Afib screening result I received from Life Line Screening different from the test I had at my doctor/cardiologist?

Why was the Afib screening result I received from Life Line Screening different from the test I had at my doctor/cardiologist?

The Life Line Screening Afib test is a limited EKG for a specific moment in time. EKGs through your doctor may check for additional rhythm problems or test for a longer period of time. If intermittent Afib is suspected, the doctor may ask you to wear a Holter Monitor so the rhythm can be measured over several days. Source: American Heart Association