when u give registeration book for token he checks for the cc and previous amount of token paid.
he justifies it to the current payable and mention.
its nothing to do with legal, or you dont need to go to some govt office, the postal office man will ask the exact amount.
i use to pay 405 rs for 87 charade and 550 for 85 charade. now guess what was the reason. both were having same engine 1000cc.
87 was standard and 85 one was 98 quota and car with quota has more token to pay
ye bhi aik science hai