AMD gave the example of Forspoken running at 4K at Ultra settings with ray-tracing enabled. Running at full native, its new Radeon RX 7800 XT GPU returns 36 fps. But with FSR scaling and Fluid Motion Frames, that jumps up to 122 fps.
Generally, AMD says that FMF can improve frame rates by over 90 percent. But that figure will vary. Depending on the asynchronous compute load of a given game, it could vary quite a bit.