collections negotiation?

[Jack25]

So I negotiated my collection account with the original creditor today pay make two payments, one for $100 next friday and $300 for the next friday. and to pay the rest of the balance on the account by the end of April($400) how can I make this arrangement work in my favor to improve my credit score? That is pretty much the last negative factor bringing my score down. Your help is much appreiciated!