This property defines the Unicodes which are Cluster Break between a base character and a following non spacing mark
Characters like 가,개,갸, etc. are listed under Prepend for Vertical Orientation Grapheme Cluster Break.
399 Characters are present in Prepend for Vertical Orientation Grapheme Cluster Break starting with the Unicode point U+AC00 that represents the character 가.
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.