extended periods threshhold

Hello,
I am working with a developer who is creating their first VR App/game. When reviewing the VRCs, in particular the VRC.Quest.Performance.1 test case. The expected results reads

The application should not experience extended periods of framerate below the requested refresh rate of the display. Exceptions include when there’s a black screen or loading scenes, or when system menu overlays are present.

We were interested in, what Meta considers an Extended Period? 5 seconds? 10 seconds?

Any information would be helpful

Thank you in advance,
Lee-Roy