SN65DSI83: The rise and fall times of REFCLK for SN65DSI83

Dear,

I have a question regarding the rise and fall times of REFCLK for SN65DSI83.

Is the rise and fall time of REFCLK of SN65DSI83 10% to 90%?
 Or is it 20% to 80%?

(tr/ tf  min 100ps max 1ns)

Sincerely,