I'm not entirely convinced this is atrial fibrillation. It may be an accelerated junctional rhythm with PACs (premature atrial contractions). I think a 12-lead ECG would be necessary to say for sure.

I would agree that the P waves are fairly obvious in the first one, while they aren't in the two that it is calling afib. That, plus the slight irregularity, is what is causing it to call it afib. However, long stretches of it are fairly regular, which would not be expected with afib (except with “regularized afib” which this is definitely not). There’s also a lot of artifact in the “afib” ECG, making it harder to interpret. However, as I don’t see any obvious P waves (someone correct me if you can find one), I cannot say for sure.

Please note that this is a single lead ECG that provides limited information. My interpretation of this ECG does not constitute medical advice. If you are concerned about your health, please talk to your personal doctor.