When does the Route Flush Timer start?

[wim4]

Hello,

It is not totally clear when the (RIP) Route Flush Timer starts.
Is it after the route becomes invalid (so after the Route Invalid Timer times out)?
Or is it when a route update is received (so when also the Route Invalid Timer starts)?

In my book (CCNA, version 5) it seems to say that it starts when the route becomes invalid, but it also says that the value of the Route Invalid Timer must be less than that of the Route Flush Timer.
That seems to contradict each other.

Thanks in advance for your answer.

Regards, Wim.