What does f-radius mean in LMI Mincx results?

As is shown in this screenshot, the mincx result states the f-radius saturation information. I wonder what this f-radius saturation information means, and how it influence the LMI results. (In this screenshot the f-radius saturation is 100% of R=1e9. However, sometimes in other case, it is only 6%.)

Answer 1

[Jingyang Mao]

https://www.mathworks.com/help/robust/ref/feasp.html