Many thanks for the clarification. Novellette? So sexy!
Perhaps then you can answer another question: when I look at a book on Kindle I see a file size in KB. My 7,200 word short story is 103KB. Are these figures a reliable guide to the length of a book in word count? In other words, would a 14,400 word story be listed as 206KB? I ask because this would also help me figure out what authors have chosen to designate their pieces of work as (novel or any other) and how much they are charging for it.
I don't think file size is a reliable indicator of length. My novel is ~66k words, but the file size is 305kb. Variations i file size can come from the program you use to write it or format it, the number of images, etc.
If there are any pictures or any kind of image in the file it will be much bigger than plain text. Same for if the cover is included in the file or not. So file size may be a clue to length, but not a reliable one.
I consider my 7700 word and 11000 word pieces short stories. I've got a 34k piece which I consider a novella. The only book I've written that I call a novel is 62k. I wouldn't count anything less than 50k as a novel. 20k-50k is a novella, IMO.