What do the large after hour spikes of 1 share each mean?

I’ve been trading for a couple years now and noticed in after hours and pre market there is always a random spike that is multiple percentages in either direction. Just wondering if anyone knows what these actually represent and if it means anything depending on which way they spike. An example would be if you go look at the NIO after hours chart right now you will see a massive spike up to 21.39 that came back down within a minute. Thanks!