Hey ER,
first of all, thank you for the purchase!
The grey italic text above the content of a page is sourced from the excerpt of the page; it can be filled in the editor mode for the particular page (in case the excerpts box is not displayed, click on the „Screen Options“ tab in the top right corner of the screen, and tick the „Excerpt“ checkbox). You can find this and other information related to the one-page website mode on page 5 of the theme manual ;)
Sincerely,
Andrii / Satori Studio