PPF calculation query..!!

The interest is calculated on a monthly basis but it is credited into the account at the end of financial year on March 31.
To maximise the benefit of investing in PPF, one should ideally make contributions before the 5th of every month in case of monthly contributions. 
becuae of this you will earn full month of interest.
I m not able to see your picture. but follow these practice to get more interest.
from next year(1-4-20) rate reduce 7.1 earlier it was 7.9