Punjab State Power Corporation [PSPCL] — bill calculation is not correct

Address: Mohali, Punjab, 140301

Website: www.pspcl.in

Dear sir/ma'am
Greetings

Meter no. 42106
Contract a/c no. [protected]

I have problem in my bill calculation. I explain below:
My last bill consumption was 232 units and bill amount was 2200rs.
Current consumption is 151 units and bill amount is 2180.
In both bills, unit difference is 232-151= 81 and amount difference[protected]= 20rs.
It means 81 units stands for only 20 rs.

Can you please solve or explain it.
I have attached my both bill's photographs.

Thank you