The Usage page shows what you have spent and where.
How do I open it?
Open Settings, then Usage. The page says "Monitor your usage and spend."
What can I change?
Period: This billing period, Previous billing period, Last 3 billing periods or Last 6 billing periods.
Day or Week: how the chart groups the time.
What does it show?
Spend over time: a chart of spend across the period.
Tables: a list of the tables behind the spend.
Good to know
For one table's own spend, open the table and choose History, then Usage history. It says "What this table spent, and on what."
The funds history on the Wallet tab lists your balance changes day by day.