This check determines whether the number of content databases in the farm is in accordance with Microsoft recommendations.
Content databases are where SharePoint stores site collections, sites and related content. Each content database is associated with the parent web application. The supported number of content databases per farm depends on the SharePoint version. SharePoint 2010 supports up to 300 content databases, while SharePoint 2013 and 2016 support up to 500.
As the number of databases approaches the maximum that can be supported, administrative actions such as creating site collections will experience a decrease in performance. When the number of databases reaches the limit, the recommendation is to use Windows PowerShell to manage web applications because the management interface might become slow and unresponsive.
Keep the number of content databases below the recommended limit. If the number goes over, SharePoint’s performance can degrade.
Additional information can be found in the following article: