Sometimes you generate a revenue by, for example, invoicing a customer, but actually this customer does not pays you right away, but later, even in installments.
You should create an intermediary asset account for your customer, then receive the incoming revenue to this account, which will increase the receivable balance you have with that customer. E.g:
This generates a total balance of 240,00 of receivables. You can attach the invoice for each transaction for your records.
When that customer pays you, you record another transaction from his account to your cash:
This zeroes your receivable balance from that customer, meaning: he does not owe you anymore.
You can have as many customer accounts as you need, and track partial payments with the invoice numbers.
So, this way, you keep track of the receivable balance for each customer.