Having the ability to Recycle Coupons is useful when using only a limited numbers of coupons. If you opt for this settings you can expect that the same coupon will be used more than once for different campaign participants. One coupon will be sent out to multiple users in a random order so that you could use 5 coupons for 100 customers rather than creating 100 different coupons.
Please note that once you run the campaign, you will not be able to change this setting. You need to choose to either have one coupon code for multiple customers or keep them as individual coupons for individual customers.
Set this option to the OFF state if your are batch uploading coupons and wish to apply a unique coupon to each participant.
Let us know how you are getting on and always reach out to firstname.lastname@example.org if you have any questions.