Is there any kind of written information from Amex for the retention offer we agreed on? Or can I find it in my account somewhere?

Amex Gold, 1st renewal, around $14.5 k spend during the year:
$100 credit or 15k MR points for $2 k spend in 3 months, chose the latter.

(Everyone else seems to have gotten $150 statement credit so either I misunderstood the agent, he misspoke or I got a lower offer for some reason. Not a problem since I wanted the MR points anyway.)