I see you asked this awhile ago so you probably have your answer by now, but I figured I'd chime in since I too have been using the Kardia device for several months now . For those who aren't familiar, it attaches to your phone and takes a single lead ekg with a phone app. It is handy for catching SVTs, Afib, etc but not a diagnostic tool for the finer points of the ekg. I used mine just to document the fact that my heart was going into random, resting bouts of tachycardia about 10xs in a month. I will say, there is a learning curve to get a clear reading. The first week or so I was still getting used to this. You need to be very still and put your phone in airplane mode (so it doesn't pick up random interference). The first few seconds of most readings will look messy from interference but after that it will level out usually. I have found it to be very accurate once I got used to using it though for me, it didn't do a good job with lead I due to my heart so I take lead II (left knee/right hand) if I want a really clear reading.
To answer your question about a crazy reading, it's either that you are still learning the device. I had loads of crazy readings at the start or that your heart does have an arrhythmia. If completely irregular with no p waves that would be afib. Obviously ask your DR though. Hope you've figured it out by now. Best of luck :).