I have several credit cards with positive balances; for example: because of refunds, etc. the bank actually owes me. But in the summary section (above the cash flow graph) the balances of all my cards show as a positive number, i.e., no negative sign, regardless of who owes who.
They are correct on the side panel to the left: if I owe the bank, it shows as a negative; if I have a positive balance, there is no minus sign.