Kerala Water Authority — complaining about previous adjustment amount

My name is suresh t v, my cosumer id is [protected], consumer no ttl/1886/d
In bill no 34208458, dated[protected] previous adjustment is 0,
But in bill no 35913402 dated[protected],
The previous adjustment is rs. 2310/-. Sir i don't understant this.
How i have previous adjustment? How you calculate this amount and on
What basis? I already paid the amount 378/- of bill no 34208458 dated[protected].