The default offset for all links in InfoSWMM is zero feet or meters. This means that the link is flush with the upstream or downstream node. There is no separation between the invert of the link and the invert of the node. InfoSWMM and SWMM 5 have another option for storing these offsets as absolution elevation. If you use the command Tools/Preferences/Operation Settings then
1. All link offsets will be stored as absolute elevations and not depth offsets. All zero depths will have the proper offset elevation if you check the flag Store Absolute Conduit Invert.
2. The Rim Elevation of the Manholes will be in absolute elevation and not maximum depth if you choose the option Store Absolute Junction Rim.