[APB5]What is this limitation about three logic levels available in timing allowances for generating parity bit?

I'm reading APB5.0 specs and while reading the parity checking chapter I encountered a ceratin limitations in parity bit. The limitation is that parity check assumes that three logic levels are available in the timing allowance for generating each parity bit? So what does it actually mean?

While researching the three logic levels are-Setup time,hold time,propogation time. Is it related to this?

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