About waking at 2:00 PM
Two in the afternoon is the classic nap alarm and a common school-pickup reminder. If you are napping, twenty minutes from this point avoids deep sleep and leaves the night's sleep pressure mostly intact.
Leave the tab open
A browser alarm can only ring while its page is open. It does not have to be the tab you are looking at, and on a desktop it does not have to be the window in front — but closing the tab or quitting the browser stops it. For anything you genuinely cannot miss, set a second alarm on your phone as a backup. That is true of every browser-based alarm clock, not just this one.