Windows Scaling Heuristics is a algorithm to identify connectivity and throughput problems caused by many Firewalls and other middle boxes that don't interpret Window Scaling option correctly.
If this setting is set to "not configured" in gpedit, then the local setting will be effective.
This setting contains two Windows Scaling Heuristics states: Enabled or Disabled.
Enabled State: Windows Scaling Heuristics will be enabled and system will try to identify connectivity and throughput problems and take appropriate measures.
Disabled State: Windows Scaling Heuristics will be disabled and system will not try to identify connectivity and throughput problems casued by Firewalls or other middle boxes.