JM: "A publisher once remarked to me that every writer had somewhere in him a certain numeral engraved, the exact number of pages which is the limit of any one book he would ever write. My number, I remember, was 385". (LRL) I wonder why Nabokov mentioned the opinion of a publisher to the point of indicating an exact number. He must have meant the original manuscript...

"I am also sending you [ ] thirty seven (37) pages of my novel The Person from Porlock...Towards the end of the book, which will contain 315 pages, there will be the looming and development of an idea which has never been treated before."

So, there's no one from Porlock to interrupt the author while he is taking down his dream ( the intruding "twang" promises him "a good night for mothing" and must be included in his 315 page counting), but Krug is! - when madness sets in and he is made aware of his creator's presence.

The project of establishing an exact number of pages doesn't preclude what Nabokov observed, and probably endorsed, concerning "the different features that are typical for ....Chekhov tales [ ] The story does not really end, for as long as people are alive, there is no possible and definite conclusion to their troubles or hopes or dreams." Krug is dead, but not the author, nor the reader, since they have become part of the novel. However, I wonder what it the idea that has never been treated before...