I guess this is table used for generation primary keys ? When you define a primary key generated by a table (@GeneratedValue(strategy=TABLE, generator="customerGen")), you will define a TableGenerator (@TableGenerator) which will create, behind the scene, a table holding primary keys. Look at the the following TableGenerator annotation:
The pkColumnName holds the name of the primary key column of the generator table (we need a pk in this table too). The valueColumnName holds the last generated value.