This line chart displays the historical balances of each currency in your portfolio, for a given period. This includes all currencies, not just your reporting currencies, before any conversions.
For each account, address and offset in your portfolio, the balances, history and transactions are summed up for each currency.
If you are looking for a table displaying only the latest balances for each currency, consider the Portfolio Balances table. If you are looking for the converted value of each currency, look at the Converted Portfolio History chart.