How do I know the sequence of execution of Managed Gateway for Spend&Network mappings?

Managed Gateway for Spend&Network will execute the mappings in the following order:

1. First, Managed Gateway for Spend&Network executes the standard out of the box mappings.
2. Next, Managed Gateway for Spend&Network executes the customized backend manual XSLT mappings done by engineering if any ( You would have raised an Ariba Case during your implementation phase requesting engineering to perform these custom backend XSLT mappings on behalf of you that cannot be fulfilled by Managed Gateway for Spend&Network Mapping Tool).
3. Last, Managed Gateway for Spend&Network executes the custom mappings done via Managed Gateway for Spend&Network Mapping Tool.

If you map the same fields via Managed Gateway for Spend&Network Mapping Tool as Engineering had mapped via backend custom XSLT mapping, Managed Gateway for Spend&Network will overwrite the Engineering custom mapping behavior with the behavior set in the Managed Gateway for Spend&Network Mapping Tool.

SAP Integration Suite, managed gateway > Managed Gateway for Business Network
SAP Integration Suite, managed gateway > Managed Gateway for Business Network SCC > Managed Gateway for Buyer Business Network SCC
SAP Integration Suite, managed gateway > Managed Gateway Foundation & Tools > Managed Gateway for Managed Gateway Portal