For "regular websites" (visited through Safari) it's 7 days where you use Safari, but don't visit the site. So if you go on vacation for a month and don't touch your computer, or if you switch completely to using Firefox for a month, localStorage will remain untouched.
I fail to see why you need to see a mention of "regular websites". The comment clarifies the situation of what occurs if a user goes on vacation or switches to another browser: nothing will be deleted, as Safari is not being used.
