In PowerPoint 2013 transition duration and transition timings are not the same. Transition time is the actual time that the slide stays active during a slide show before moving on to the next slide. Transition duration is the amount of time it takes to move between slides. Normally, during slide show, you can advance to the next slide by mouse click (or pressing the Enter key on your keyboard). Using transition timings on the other hand, you can set your slides to advance on their own instead, and display each slide for a specific amount of time that you decide.
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