L2B visa PED & VISA expiration dates different from L1B

I got my L1B visa stamped last year and recently in September,2018 applied for L2B for my dependents. Thier visa got approved.

But after receiving thier passport ,I realized that the PED & VISA dates are different from my VISA. since I applied in 2017, PED and visa expiration dates are in 2020,and my dependents applied in 2018 thier expiration and PED dates are in 2021.is this normal &ok?