CONSPAN Flared Girder Alignment Dialog

Hi, guys, I have a question regarding "Bridge Alignment" for "Flared Girder" in CONSPAN.

The help file tells "CONSPAN assists the design by computing the distance between supports along the centerlines of the bridge and, if desired, along the centerline of each girder."

I can understand how to define the centerline horizontal curve as in the following picture. However, please teach me how to define the support distance for each girder.