The third chart in the bottom section, shows the load on the PostgreSQL database system, in terms of overall amount of time taken by each query in a database.
Each bar represents the overall time taken by a query i.e. sum all of its execution times.
The load is measured in terms of units of time taken by a query to execute.
The X-axis represents the query identifier and the Y-axis represents the time taken to execute.
Hover over the bar for more information.
Longer the peak of the bar, more time a query has taken.
If you feel like any query shouldn't have consumed as much time in all its executions, fine tune it as necessary.