I have an EVK4 device, when I use python's EventsIterator to read the events generated by the device, the delta_t is 10ms, and other parameters are the default values, but I found that when the brightness of the picture captured by the event camera does not change, the negative time generated is always more than the positive events. My measurement found that for each frame of data, there are about 50,000 more negative events than positive events. I don't know why this phenomenon occurs. Can you explain the reason for this phenomenon?