Basically, this mostly means some VHF
channels will have a prefix of "10" in front of the number we (in the US) already see on our radios.
The international system has more duplex channels (receive and transmit on different frequencies.) This is more appropriate for communication with a shore-based relay system, which (at least in the US) isn't used much.
Now, numbers displayed on both US and international settings will mean the same thing.
Not much action needed by the average recreational boater. If you see or hear a "10" in front of the channel number, that only means it's simplex, not duplex.