I read about duplets in "Music Theory for Dummies" by Michael Pilhofer and it was introduced with the following graphic (not exactly the same - it should be interpreted as a rhythmic notation).
The counting for this rhythm is given as
ONE two three FOUR-and ONE-and FOUR five six
The way I understand tuplets is that they have a 2:3 ration, meaning two notes take the place of the normal three.
But I cannot makes sense of the counting, especially that there are two bars in the example. I would have expected to count twice to six - two bars with six beats each.