Tamil Nadu Electricity Board [TNEB] — Excess Bill without reading

We have received a Bill for the Month of May 2021 of Rs. 9040. for 1600 units stating " Previous Assessment Amount Billed".

But our last bill reading dated 22nd March 2021 : 24380
Reading as on 26th May 2021 : 24997
Total units consumed : 617

Almost 1000 units extra, for the last one year, our billed amount is around Rs.1000.

How can for 617 units bill amount is 9040.

Attaching all the screenshots for reference.