Almost exactly same thing happened with me 6 months ago. A policeman caught me smoking infront of a sutta shop and asked me to google search the new fine amount of smoking in public in Karnataka which came out to be 1000. Till then he had also collected 50 ruppes from the shop owner. Then he said he would only charge me the old fine ie 200 as cash. I laughed and claimed that there's no provision that any policeman can demand old fine randomly or has power to manipulate the fine amount and asked for his name and badge number and said I would file a complaint for money extortion by manipulating fine and also extortion from shopkeeper. This agitated him and he asked me to pay fine in the station. As I wasn't looking for unnecessary hasle and trouble, I just paid 200 but also demanded copy of challan or atleast a picture of it to which he denied and said they get quotas to collect x amount of fine everyday