This property defines the Unicodes which belongs to Combining Half Marks block
Characters like ︠,︡,︢, etc. are listed under Combining Half Marks Block.
16 Characters are present in Combining Half Marks Block starting with the Unicode point U+FE20 that represents the character ︠.
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.