Scratch that. Per the link I just posted:
Are there any other limits or restrictions that apply?
Yes, the OPEN Savings® discount per American Express OPEN Business Card account has a combined savings cap of $3,000 broken down as follows:
Maximum annual discount of $1,000 for FedEx Express® and FedEx Ground® shipments
Maximum annual discount of $1,000 for FedEx Freight® shipments
Maximum annual discount of $1,000 for FedEx Office® purchases
$1000 won't go very far for me.