This property defines the Unicodes which belongs to Bopomofo block
Characters like ㄅ,ㄆ,ㄇ, etc. are listed under Bopomofo Block.
44 Characters are present in Bopomofo Block starting with the Unicode point U+3105 that represents the character ㄅ.
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.