I think that “other rhythm” is a tricky measure. The algorithm analyses your ECG and tries to determine if something is outside the periodical rhythm of your heart. The analysis is done after the recording. Doing a bit of reverse engineering, the formula for calculation is %NOR = #NOR * 100 / (3*TT), where #NOR is the total number of “other” and TT is the total time of the recording in minutes. So, if you have one single “other” in the 20s recording, the percentage takes all 20s as “other” in the calculation of the %. About the interpretation, it’s difficult. The deviation from the standard can be related to multiple factors, in some cases not directly correlated with the heart function, like movements, fasciculations, interferences and so. But it can also reveals PVC or other heart anomalies. In essence, 17-20% when you sleep seems a bit high, but you should analyse how clean is the wave recorded before draw conclusions, and also after, it is difficult to conclude something. If you are concern, the best way to clean up the doubts is a 24/48h Holter. However, if you did ECG recently and all were good, it should not be a problem. Cheers.