Thanks for that thorough explanation as I was having the same confusion.
One follow up question: If I program in a CTCSS tone on item 1 T-CDC then program in a different CTCSS tone on item 2 R-CDC then item 3 RT-CDC automatically populates with the same CTCSS frequency as item 2. When this happens is the T-CDC value no longer used? In other words is this radio incapable of joining a repeater with different TX and RX CTCSS tones?