The US Coast Guard has a nice chart of the numbering changes on some of the VHF marine radio channels used in the United States. Here is a link to the chart:
https://www.navcen.uscg.gov/?pageName=mtvhf
So why the changes? Here's an explanation from the Coast Guard:
Note that the four digit channel number beginning with the digits "10" indicates simplex use of the ship station transmit side of what had been an international duplex channel. These new channel numbers, now recognized internationally, were previously designated in the US by the two digit channel number ending with the letter "A". That is, the international channel 1005 has been designated in the US by channel 05A, and the US Coast Guard channel 1022 has been designated in the US as channel 22A.
