Hi @Uma Maheswara Rao Desula​ 

thank you for the response!

I have checked the real size of the loaded dataset and it was a little bit more than 103 GB. Using you fomula:

(103,1*1024)/128 = 824,8

This is why in the exercise there was 825 partitions and then, as you pointed out, the closest factor of 8 is 832.

Now everything is clear for me - I like to know exactly why each metric was selected 🙂

Cheers

Bartek