This property defines the Unicodes which belongs to CJK Unified Ideographs Extension B block
Characters like 𠀀,𠀁,𠀂, etc. are listed under CJK Unified Ideographs Extension B Block.
42720 Characters are present in CJK Unified Ideographs Extension B Block starting with the Unicode point U+20000 that represents the character 𠀀.
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.