DoCmd.TransferText rounds single numbers

Hi,

I am using the command below for exporting data to text file. One of
the query columns has SINGLE number type with decimal ponts as auto.

DoCmd.TransferText acExportDelim, vnp_export_specification,
vnp_export_query, vnp_export_file, False

Some values like 0.6678 when exported to text file become 0.66 and
values like 0.0006614 remain the same.

What could be the reason for some values to be rounded and some not ?

Thanks a lot.