Map Error, Help me to fix it please.

Hi,
I am learning BizTalk Map.
I am getting the following error when i build the project. Could anyone help me
to fix this?

Record "PayLoad" – If preserve_delimiter_for_empty_data is false
and suppress_trailing_delimiter is true or preserve_delimiter_for_empty_data
is false and suppress_trailing_delimiter is false, the serialized data might
not be able to be parsed using the same schema unless all children are either
optional or tagged.

I am getting this kind of error for 2 top level records in Flat file.