The WSO2 APIM 2.6.0 statistics are not displayed in the APIM Analytics 2.6.0 dashboard, rather as same as the previous product version it is displayed on APIM 2.6.0 Publisher profile. underneath implementation directly access the Store Query AP in APIM Analytics 2.6.0 Worker runtime in order to get the statistics data.
So, in the default analytics scenario, you don't need to deploy the APIM Analytics 2.6.0 dashboard runtime to view the APIM statistics.
To give an answer to your query, unfortunately, there is a limitation in dashboard runtime with Postgres SQL where we need to introduce the compatible queries in here: https://github.com/wso2/carbon-dashboards/blob/master/components/dashboards/org.wso2.carbon.dashboards.core/src/main/resources/sql-queries.yaml
or else you can give the compatible queries in the wso2am-analytics-2.6.0/conf/dashboard/deployment.yaml as explained in the doc:
https://docs.wso2.com/display/SP430/Configuring+Database+Queries#ConfiguringDatabaseQueries-DashboardDashboard
Copy the queries with the above structure under the 'wso2.status.dashboard' namespace.