The Zone, Airloop, and Facility component loads summary reports are all structured in a similar way. First there is a large table of "Estimated Cooling/Heating Peak Load Components". Below that is a smaller "Cooling/Heating Peak Conditions" table. The question here asks about these two lines in the Peak Conditions Table

Peak Sensible Load [W]  -13845.7
Estimated Instant + Delayed Sensible Load [W]   -13793.7
Difference Between Peak and Estimated Sensible Load [W] -52.0

The "Peak Sensible Load" is the actual peak load from the zone sizing calculations using the full zone heat balance.

The "Estimated Instant + Delayed Sensible Load" is the equivalent total from the estimated load components table (sum of the first two columns).

"Difference Between Peak and Estimated Sensible Load " indicates how good the component estimates are. The components are estimated in a side calculation which attempts to separate the full peak load into it's various components.

Also see "Component Load Summary" in the Input Output Reference.