Один пробел добавляется в конце при вставке данных в БД?

While inserting data into a table using .Net entity framework stored procedure call a white space is appending at the end. this issue is with two columns only.
where both the columns are having a Foreign Key to different tables (the tables will have allowable values (constants)). 
FYI.

 1. column 1 is defined as varchar(6) and column 2 is defined varchar (3) in sql DB.
 2. but the foreign  key table 1 is having data with max length is 4, table 2 is having data with max length is 3.
 3.  in EDMX file below code is available 

a) 

    <Function Name="spInsertdetails" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo">
            <Parameter Name="column1" Type="char" Mode="In" />
            <Parameter Name="column2" Type="char" Mode="In" />
    
    b) <FunctionImport Name="spInsertdetails" ReturnType="Collection(TestDBModel.spInsertdetails_Result)">
                <Parameter Name="column1" Mode="In" Type="String" />
                <Parameter Name="column2" Mode="In" Type="String" />

Please let me know if any further details required.

in 3.a) i have tried changing the char to varchar but the issue still present.