How do reads per chapter work

As the title says, how do reads per chapter work? I have over 20 chapters published on my ongoing work and I completely understand if the first chapter has way more reads that the other chapters because if people click in, they proceed only if they are interested, but what about other chapters? For example, my 6th chapter has 98 reads while the 5th has 71 reads. After the 6th, the reads per chapter decrease and go back up to 88 reads on the 21st chapter. All the chapters in between waver between a low of 40 reads and a high of 70. How does it work and what does it mean? Do people specifically choose which chapter to read or...