Using the “Frame Range” process method you can specify a Start and End frame, and how many samples you want.
Then FrameMedian distributes samples evenly across that range.
You can also use the “Specified Frames” method, that allows you to specify what frames you want to sample.
For the best result the input plate must be stabilized and not have too much chroma/luma alteration. So in case of Day-to-Night timelapses pick frames/frame range within same light.
Due to the nature of the median function more samples is not always better, so its good to try out different frame ranges and sample count.