Here is the recent case about ticket errors: courts-and-procedure/cops-can-fix-small ... t7933.html
In my opinion, an incorrect set fine amount would be considered minor and it is not prejudicial towards the defendant in preparing a full answer and defence to the charge.
With the new case, the police officer can correct the set fine amount on the certificate of offence (his copy of the ticket) and still submit it validly to the courthouse. This means if you do not respond, you will be found guilty. Upon appeal, you will need to be able to argue how an incorrect set fine amount is prejudicial towards your ability to make a full answer and defence - this will be difficult.