"Partial" amount - what is this exactly for?

In an invoice, there is the “Partial” field. If I have an invoice with an amount of, let’s say 1000,-, no taxes, and I fill in 300 into the partial field, the end sum down on the invoice is now 300,-

But how is this meant?
I suppose it’s the partial amount the client has to pay now - but how do I invoice the rest of the bill? If I enter a Payment of 300, how does this show up under “already payed”?

Could you explain shortly how to use this “Partial” feature? I found nothing in the documentation.

When a client makes a payment online by default they’re shown a ‘Pay Now’ button with the full amount of the invoice.

The partial feature lets you set how much we should bill your client when they try to pay. When the client makes a second payment it will bill the remaining amount.