This property defines the Unicodes which should be treated as a starting base character of a grapheme cluster
Characters like ᄀ,ᄁ,ᄂ, etc. are listed under Base Grapheme Cluster Break.
125 Characters are present in Base Grapheme Cluster Break starting with the Unicode point U+1100 that represents the character ᄀ.
Currently, as per latest version 15.0.0, Unicode supports 14 number of Grapheme Cluster Break. Here are a few examples - Base,Carriage Return,Control Neutral, etc.