This property defines the Unicodes which belongs to Math Alphanum block
Characters like 𝐀,𝐁,𝐂, etc. are listed under Math Alphanum Block.
1016 Characters are present in Math Alphanum Block starting with the Unicode point U+1D400 that represents the character 𝐀.
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.