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[Myself °¿°]

still working on the lingo. When using letters... are they for corrective labeling?

abc for 3 waves and abcde for 5 waves... I understand.
...but don't know when to use them.

Don't know when to use roman numerals, lower case letters, upper case letters, numbers and circled numbers.

I know they should be used to limit confusion but I can't find it.