It's not clear for me, which voltage your referring to. Input DC voltage is Vin,peak minus some ripple, output is 5 V DC.
The input filter apparently is intended to reduce interferences but can't change the DC levels. Basically it's a Powerint
application circuit, AN-37 http://www.powerint.com/sites/default/files/product-docs/an37.pdf shows a lot of
calculations related to circuit dimensioning.
The Lin and C1,C2 dimensioning isn't discussed in AN-37 and the underlying design considerations aren't that obvious.
But the inductor can't have a noticeable effect on conduction time, thus I think, it's intended for reduction of
switch-frequency interferences.