Hey there! Dan from the AMZ Tracker crew here. I saw your post on the forum, and that's actually more of a support issue than something that should be asked of the community. We like to keep the forum focused on seller discussions, so in the future, please just hit us up at [email protected]
with questions like this. But for now I'm happy to take care of you here (and sorry for taking a few days to get back to you here)!
There IS danger in leaving "One redemption per customer unchecked", and we strongly recommend against doing that. If the promo codes that you send out give a percentage discount, then one customer could claim as many units as they want with that one code, and the discount would count towards the full purchase.
Also, keep in mind that a reviewer can’t leave a review on different variations of a product, so there's no benefit to giving out multiple codes for variations on the same product to one reviewer.