Only New Zealand GST that has been charged can be claimed back. This does not include the purchases you have made overseas. Make sure to click Add Details and change the GST to No GST when reconciling.
If you are importing goods into New Zealand, there may be GST that can be claimed. Look out for costs with and without GST when looking at costs such as overseas/NZ freight and insurance and admin fees. If there is claimable GST, code appropriately with 15% of GST, and if not, with no GST.
If there are GST that the customs have charged for imports, code to GST on Imports.