The central chart on the Account Journey Dashboard is the "Accounts by Journey Stage" chart:
Bar Chart: Accounts by Journey Stage

The Journey Stages are indicated on the left of the chart and follow the Stage Order:

The numbers and the chart shows how many Accounts there are in each Journey Stage:

The (%) Percentages show the % that Accounts in each stage represent out of the total number of Accounts in the Account list.

The total number of Accounts in the Account List is shown right above the chart:

And the Account List can be changed using the Account List Picker: