This property defines the Unicodes which belongs to CJK Unified Ideographs Extension A block
Characters like 㐀,㐁,㐂, etc. are listed under CJK Unified Ideographs Extension A Block.
6592 Characters are present in CJK Unified Ideographs Extension A Block starting with the Unicode point U+3400 that represents the character 㐀.
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.