I am running Viewshed with 500 points and a floating point DSM clipped raster with elevation values from 5.5 to 173.36 meters. The Viewshed output raster appears to be compliant with the surrounding area however for visibility however the Above Ground Level raster is mostly a large negative value. I have modified and removed OFFSETA and OFFSETB fields from the 500 Point feature attributes but continue. There appears to be a sliver of positive values that runs from off in one direction from a few of these points. Grid_Code Field is all 0's though I don't think it is built into the tool's script.
I previously ran Viewshed with a different point feature with OFFSETA and OFFSETB, and received a more accurate assessment of the Above Ground Level raster, with 0 for Visible areas.