At the beginning, click on any type of note (one note, two notes, triad, or seventh chord) to change its capability to be generated. Then choose how many notes you would like to generate.
Seventh chords will be displayed exactly the same as triads, save they will have an "extra note", which will be the interval between the third note on the triad and the fourth note altogether (making in a seventh chord). For example, if [root:c | triad quality: major | extra note: minor 3rd | rhythm: 16 sixteenth notes] is shown, the result is actually a c domenent 7th chord.