This property defines the Unicodes which belongs to Phonetic Extensions Supplement block
Characters like ᶀ,ᶁ,ᶂ, etc. are listed under Phonetic Extensions Supplement Block.
64 Characters are present in Phonetic Extensions Supplement Block starting with the Unicode point U+1D80 that represents the character ᶀ.
Currently, as per latest version 15.0.0, Unicode supports 328 number of Block. Here are a few examples - Latin Extended E,Adlam,Aegean Numbers, etc.