American Express settlement

I have two account with AE; one for 19000 and other for 17000. It have sent to NCO after 120 days. Few days after send to NCO, I am able to make 30% for 3 payements on 19000. But I wanted 4 payments so the guy decide to call me back next day. I was then offer 25% for two payments on the 17000 account by difference person from the same group. And it was approved. I believe it is a good offer so I accept it. However, I won't be able to accept the 30% offer anymore. I was hoping they will come down to 10-15% for the 19000 since I really don't have money to settle more than that. It 10-15% relistic for AE settlement? Anyone ever got that offer for 120 days late?
I want to thank this forum for all the great post. I was almost go for settlement company. Instead, I DIY and I will be almost out of debt within 6 months.