Double Bass REALLY Learning a tune

[Ed Fuqua]

After D F A C, the closest note from G7 would be, going down, the B (on G string). But going up the D (1 tone away from C, on the G string). If you go to the D you started with again, isn't that a change of octaves?

This is what I don't understand...

This is what I don't understand, why do you think it changes octaves? The D is the same pitch (open D string), the F is the same pitch (F on the D string), then open G string, then B on the G string. Think proximity, you're looking for a fingering that keeps the most common pitches (D and F are the same) and movement of the other 2 pitches to a half step or whole step. The A moves down a whole step to the open G string and the C moves down a half step to B.
Is that any clearer?

If you move up a whole step from the 7th of D minor (C), then you are keeping NO pitches in common so, for the purpose of this exercise, WHY would you do that? I don't understand why you say "the closest note from G7 going down..." when what the exercise outlines is playing a 2nd inversion dominant chord (fifth, seventh, root, third).
Maybe I'm missing something...