"Additional fines" refer to extra penalties or charges that are imposed in addition to the original fine. It means that there will be more money to be paid on top of the initial fine as a punishment for the offense committed. Full definition
Failure to do so will result in additional fines, penalties and license suspension. (toocooltrafficschool.com)
You don't want to miss a court deadline, as you could face additional fines and penalties. (idrivesafely.com)
If you can retain your driver's license or avoid additional fines by paying the money you owe immediately, this is always a better option. (simplethriftyliving.com)