Simple question about coupons on M2

Hi there, I have a quick question. On this site I have a coupon that is a lifelong free coupon. The user is able to sign up fine and use the coupon fine and it says free so that's all good... but then on the backend of the site it says in the coupon, 0 used out of 30 limit, when 3 people have used it. Is that because of something I've set up wrong? Thanks.