ESD441: Leakage current

Part Number: ESD441

Hi,

In the data sheet: Iio<100nA at Vrwm=-5.5V ~ +5.5V.

Q1: This is a unidirectional TVS. Why does it specify -5.5V ~ +5.5V?

Q2: Ileak=50nA(max) at Vio=5.5V. Why does it state Iio<100nA? 

Thank you,

Thomas