This property defines the Unicodes which are Tone Letter
Characters like ᥰ,ᥱ,ᥲ, etc. are listed under Tone Letter Indic Syllabic Category.
7 Characters are present in Tone Letter Indic Syllabic Category starting with the Unicode point U+1970 that represents the character ᥰ.
Currently, as per latest version 15.0.0, Unicode supports 36 number of Indic Syllabic Category. Here are a few examples - Avagraha,Bindu,Brahmi Joining Number, etc.