For comparison, since I believe in transparency:
Liminal Radiance - Path Of Old Dreams
Chapter - Title - Readers
1 - Creatures in the Fog - 719
2 - Unlikely Allies - 458
3 - And they were legion - 313
4 - At the gates of madness - 198
5 - The forlorn Muse - 195
6 - House of the Inspired - 194
You can see the sharp initial decline and it then settles in. After that, it's a slower decline as people need to catch up with newer chapters or lose interest half-way in. Others mark it and come back later. Maybe some aspect in the story sets them off or they realize it's not what they want after all. On a sidenote, sometimes it's just a random part of the story that ticks them off. I had a chapter where one of the main characters had an allergy towards meat. Oh joy, that went over really well - I saw angry comments about vegan agenda and soy boy fiction outside of royalroad.
1) Aftermath and Prelude, 2040: 6152
2) Midsummer's Eve, 2040, preparation of the traditional garden party: 4231
3) Prologue, 2015, September: 3583
4) Midsummer's eve, 2040, seating the guests: 3160
5) Chapter one, 2016, schoolstart, part one: 3240
6) Chapter one, 2016, schoolstart, part two: 2886
7) Chapter one, 2016, schoolstart, part three: 2122
8) Chapter one, 2016, schoolstart, part four: 2187
As you can see the 'chapter names' give an indication of where the story settles into a recognisable pacing and from there on the readership numbers slowly drop until it reaches:
Epilogue, 2016: 1810
which would be something like 'chapter 41' or so.
Add retention if you decide to write a series. That one is more brutal since you force your readers to start a 'new book'. For example between Epilogue book one and Epilogue book two I dropped half my readership, and by the time I finished book five I was down to a mere ten percent compared to the ending of book one.
My prologue is very short and is designed to be a "hook" so it gets a high retention rate. Still, the views drop sharply at chapter 3 as the story becomes slower.
views Retention rate
Ch 0 1,300 100 %
Ch 1 1,206 92.8 %
Ch 2 1,010 83.7 %
Ch 3 971 96.1 %
Ch 4 785 80.8 %
Ch 5 665 84.7 %
Ch 6 587 88.3 %
If you think your prologue got low retention rate, then I think you should try to shorten your prologue. Make it around 500-750 words and make it interesting and mysterious since readers love mysterious things in general. Still, this is only an advice from an LN reader and a rookie writer.