delaySeconds

The length of time, in seconds, for which a specific message is delayed. Valid values: 0 to 900. Maximum: 15 minutes. Messages with a positive DelaySeconds value become available for processing after the delay period is finished. If you don't specify a value, the default value for the queue is applied.

When you set FifoQueue, you can't set DelaySeconds per message. You can set this parameter only on a queue level.