How to deal with asymmetric FOV

After read ,I know how to deal with symmetric field of view,But I dont know how to deal with asymmetric FOV,In struct XrFovf,which one should be negative,angleLeft or angleRight?
angleUp or angleDown?And the Specification said that: ‘When angleLeft > angleRight , the content of the view must be flipped horizontally. When angleDown > angleUp , the content of the view must be flipped vertically’.Does that mean that the app view on pc will upside-down?

So the “must be flipped” is a feature to allow apps to specify their content needs flipping, and can be ignored in most cases.

The docs say “for a symmetric field of view this value is negative” to be precise. In reality, the elements noted as negative for symmetric fields of view are also negative nearly always. (Especially in a two-view HMD case, I can’t think of an example where an HMD designed for a human user would not behave this way.) However, because you could have a FoV entirely to the right of center, theoretically, we condition the statement on the FOV being symmetric.

Left and right are locations along an axis, not magnitudes from a center. Similarly for up/down: locations along y axis, not magnitudes.