Also called custom business logic, these are the steps that might take several individual calls to the CryptoServer. Because the CryptoServer may be many hops away (network topologically speaking), a single call may be "expensive" in terms of time or even cost (cloud data charges).
Instead of making these several calls individually, the SDK user can supply all the various inputs to a single custom firmware SFC call, and receive at the end of processing the final result they are targeting.