Sometimes marketing emails get flagged as spam. This can happen for any number of reasons. However it is important to keep an eye on this metric so that you can keep the number of spam reports and spam report rate at a minimum.
Higher spam report rate may result in ISPs taking action and directing your email to the spam folder instead of the inbox. If the rate continues to be high, your emails may even get blocked by the server.
Keep an eye on this metric and if you see a sudden spike in spam report rate, look in to the most recent emails and its recipients to make sure you are targeting the right audience for your emails.