As you can see there is no black key between E and F and thus there's only 1 semitone between the notes. This makes the interval a minor second (which you will learn about at a later stage in the app).

Try reading more carefully in the wiki or watch the video again, it clearly states that:
a major second is an interval from a natural to the next one above it, provided that there are also 2 semitones between the notes.