Bangalore Water Supply & Sewerage Board [Bwssb] — irrelevant billing charges

Address: 560072

The water bill which i have recieved is too high for the litres consumed.
In the previous bill the amount was 400 rupees for 2600 lts.
This month the litres consumed is 2700 and the bill has come upto 2800???.
What's the math here. Does the bbmp department have a special formula?

We paid 2800 rs in january too.
Please do resolve this issue asap.