This will set the limit for the amount of dashboards you can create. Quotas are very simple to grasp, they are the sum of intersections you have in a dashboard.
Look at this example here:
This dashboard's capacity is visible on the top right part of the dashboard. There are 40 intersections, meaning this dashboard capacity consumes 40 points out of the account's total credits.
Adding a third dimension to your dashboard will multiply the intersections by 2 or 3 depending on the amount of variables you have selected.
Here is an example:
In this dashboard, you will see a filter under the dashboard name. Meaning that the user can switch from Asia, to Europe or North America.
Hence, the capacity for this dashboard is 40 points x 3 = 120