Oracle Data Type: NVARCHAR2 - Column sizing is wrong

Create table like so and notice the 255 size:

CREATE TABLE TESTNVARCHAR2( NVARCHAR2_NULL NVARCHAR2(255) NULL, NVARCHAR2_NOTNULL NVARCHAR2(255) NOT NULL, NVARCHAR2_DEFAULT NVARCHAR2(255) DEFAULT 1 , NVARCHAR2_PK NVARCHAR2(255) , NVARCHAR2_UNIQUE NVARCHAR2(255) , CONSTRAINT PK_NVARCHAR2 PRIMARY KEY (NVARCHAR2_PK) , CONSTRAINT UN_NVARCHAR2 UNIQUE (NVARCHAR2_UNIQUE) );

Take snapshot and notice the size is now 127:

<changeSet author="robert" id="1382988622897-18">
<createTable tableName="TESTNVARCHAR2">
<column name="NVARCHAR2_NULL" type="NVARCHAR2(127)"/>
<column name="NVARCHAR2_NOTNULL" type="NVARCHAR2(127)">
<constraints nullable="false"/>
</column>
<column defaultValueComputed="1" name="NVARCHAR2_DEFAULT" type="NVARCHAR2(127)"/>
<column name="NVARCHAR2_PK" type="NVARCHAR2(127)">
<constraints nullable="false"/>
</column>
<column name="NVARCHAR2_UNIQUE" type="NVARCHAR2(127)"/>
</createTable>
</changeSet>