dspdfviewer is intended for presentations created with the latex-beamer class, specifically documents created with the show notes on second screen=right option.
Its purpose is to display the left half of a page on the audience’s screen (which will most commonly be a projector) and the right half on your "private" screen (think: the notebook you carried to the presentation site). The basic idea is that you will display personal notes and information to help you with your presentation on your personal screen, while the audience sees only the PDF they are supposed to see.
On the secondary screen you will see three clocks: A "wall clock", a "presentation" clock and a "slide" clock.
The wall clock in the bottom left corner that display current time of day, the presentation clock (labeled "Total") counts the time you spent since you started the presentation, and the "slide" counter (bottom right) displays the time you spent on the current slide.
The clocks don’t start the second you launch the program, the idea behind that behaviour is that many people have a "title" slide active long before the audience even arrives.
Once you use the next/previous slide commands, the clock starts. If you want to start the clock, but still display the title slide, just press "previous" (for example, Up Arrow or Right Mouse Button) on the title slide.
If you want to reset the clocks to zero, press the "Home" button on the keybord.