What do the numbers in the export file name mean?

The naming criteria for all exports is the same and is explained below.

PurchaseInvoices-731-134223-1-0-0-29052016.csv

In the above example:

731 - the export ref number for that specific export

134223 - the time is was run. This export was done at 13:42:23

1 - the company ID

0 - the Area ID. This is 0 is run for all areas

0 - the Outlet ID. This is 0 if run for all outlets

29052016 - this is the week ending date. This export was run for the week ending 29th May 2016