If you are processing Open Item matching, and you are correctly matching receipts against the relevant invoices, then your statement should only reflect the unmatched (outstanding) invoices.

If you are processing with the Balance Forward method, then make sure you select only the current period in your period range, e.g. May 2015 to May 2015. Any outstanding balance prior to May 2015 will reflect as a Balance Brought Forward line item at the top of the statement.