I haven't looked at the underallocated report in detail yet but the overallocated report is quite broken and I have an open case on this. The query is based on active memory but the recommendation is based on consumed memory so it's not unusual to see it recommend an increase in the report.
Have a good look at the query and then look at the calculation for the underallocated report and also look at the XML to see if the recommendations make sense in your environment. You can, and probably should, customize the recommendation because it seems like SolarWinds took a VERY simplistic approach to the recommendations.
