The balance is correct. When a pledge is split among funds (campaigns or appeals), any scheduled installments are split among the same funds (campaigns or appeals) using the distribution of the pledge. Even if payments have been applied to pay off one specific split fund (campaign or appeal), the remaining balance is still distributed among all funds (campaigns or appeals).

If you would like to show the pledge balance by fund, campaign, or appeal, add a pledge for each fund, campaign, or appeal.