Oracle Insert Into NVarchar2（4000）不允许4000个字符？

I have a table with a field datatype of NVarchar2(4000) I am moving data from a SQL Server to an Oracle Server. The SQL Server datatype is also nvarchar(4000). I have checked the MAX Size of this field on the SQL Server side, and the MAX is 3996, which is 4 characters short of the 4000 limit. I have a table with a field datatype of NVarcha