Runtime Replacement Tags are evaluated after component finishes execution. They are only available to subsequent components in a workflow.
When you create a task that consists of a series of components, the components are executed in workflow order (Capture → Process → Route). Prior to completing execution, each component in a workflow searches all configuration entries and replaces its own RRTs with actual run-time values. For example, the Send To File component searches for RRT strings starting with ~STF:: and replaces them with values specified by their RRTNs.
RRTs available to a component depend on the order of execution of components in a workflow. Component RRTs do not become available until after a component finishes execution. RRTs owned by components that appear later in a workflow cannot be placed within components that appear earlier in the workflow. For example, the Send to Folder component is a Route component, so Send to Folder component RRTs are invalid in a Process or Capture component. If you were to type a Route component RRT into a Capture or Process setting field, it would be undefined at run time and not return any value.