This property defines the Unicodes which are Gemination Mark
Characters like ੱ,ૻ,𑈷, etc. are listed under Gemination Mark Indic Syllabic Category.
4 Characters are present in Gemination Mark Indic Syllabic Category starting with the Unicode point U+0A71 that represents the character ੱ.
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.