I beleive 52-17 is becaus (52+17)*7 =~ 8 hours
I had a big problem with procrastination before. I wasn't able to concentrate, find it difficult to retain focus and most of the time I had to stay a couple of hours more to finish my daily tasks.
So I did a research to find a cure. Here are some of the things I did to boost my productivity and focus:
Do NOT multitask - like Jan Vladimir Mostert mentioned, concentrate all your power on one task at a time. Switching between different problems and tasks is counter-productive!
52-17 rule - this one is pretty interesting and simple - work for 52 minutes, rest for 17. It's simple as that. It's like mini sprints - during the 52 minutes work, you're dedicated to complete and accomplish tasks and make progress. Then, for 17 minutes you are entirely resting, moving away from the desk and just relaxing. You will be amazed with the results!
Find the right music for YOU - find what kind of music works best for you no matter electronic, classical or rock. I have days when I listen Sweet Home Alabama or similar, the next day I play Get Lucky by Vitamin String Quartet. It's personal choice at first.
Document your progress - this is something I practice lately and I see great results. Document your current progress, make a daily task list and just write what you have done. It will give you a clear vision of your productivity status.