EDI----ConvertoValues

Hi Folks,

I am new to EDI, i am getting a problem when converting a EDI to Values…
The problem is in the ST loop (ConverttoValues).

Error Message:[FFP.0011.0003] Unexpected element. The record or composite data contains more fields than are in the record or composite definition.

The Input data is correct.
when i am using the convert to Values under GS loop it is working properly.
but Under ST it is showing the error, and i am not able to extract the first record after the ST, the rest of all records are coming.

Please…any one help me to find the solutions …as it is very urgent for me.
any suggestion will be appreciated