I have had to show the experience recorded as extended in time

My 1950 edition of Proust's letters is the colour of our third-hand sofa. The only annotations in the book occurs on the page opposite a black and white reproduction of Whistler's Comte Robert de Montesquiou-Fezensac portrait, where a previous owner has made pencil corrections in handwriting that is so like my grandmother's I have been trying to imagine her taking such an interest in this 1912 letter to Antoine Bibesco that she would want to correct Mina Curtiss's translation, with Comte Robert Montesquiou-Fezensac's raised right eyebrow challenging her to comprehend Proust's reference to jeunes filles in his letter to Georges de Lauris in 1908 -- this grandmother of mine who, for all I know since I hardly remember her, had been the one to insert a footnote in the following section:

There are novelists, on the other hand, who envisage a brief plot with few characters. That is not my conception of the novel. There is a plane geometry and a geometry of space. And so for me the novel is not only plane psychology but psychology in space and time. That invisible substance, time, I try to isolate. But in order to do this it was essential that the experience be continuous.

Between and a little above the words 'experience' and 'be' in that last sentence my grandmother has written an encircled number one, and at the bottom of the page the footnote reads:

I have had to show the experience recorded as extended in time.