Here is a simple chart that tells you the bill generated for the electricity consumption.
Unit (1Kwh) is given in Top as well as in the left side.
For example, if the number of units consumed is 480,
Locate 400 in the top and 80 in the left side, see the corresponding amount which is Rs. 1270.
I have taken this chart near a ration shop in Chennai.
you can verify yourself with this consumption.