ID3D11Device::GetFeatureLevel

DX11 vtable[37] → D3D_FEATURE_LEVEL

ID3D11Device::GetFeatureLevel is a method of the COM interface ID3D11Device in Direct3D 11. Its function pointer sits at vtable index 37 — the zero-based slot in that interface's virtual method table, counted from QueryInterface and including every entry inherited from a base interface. It takes no parameters and returns D3D_FEATURE_LEVEL.

COM methods are reached through that table rather than by an exported name, so the slot index is what a wrapper, an interface hook or a disassembly listing has to resolve against.