There are 2 elements under this section. 1) is capping the number of claims and 2) what is the maximum number of claims available.
1) capping the number of claims simply means, do you want to have a limitation on how many users may qualify to claim?
2) how many rewards do you have available to be claimed? if you have 50 UberEats vouchers, then you will fill in 50
What you would have already pre-determined is your perk module type. For competition you would not cap the number of entries as you would encourage as many entries as possible.
For coupon code on the other hand, if you only have 100 coffee vouchers to distribute to your users then it would make sense that you have to cap the number of claims, and in this case, the maximum number of claims would be at 100.
*If you do not cap the number of claims for coupon perk, you might end up "giving away" more coupon codes than you have, so make sure to pay attention to this.
For URL link and freeform, they have different purposes. E.g. for the URL link you are driving your users to a specific landing page so capping the number of claims might not apply to you, it really depends on what you are trying to achieve.
For freeform, you might use that to give users different instructions e.g. to download your app before unlocking their reward, therefore in this case, you would select "No" for capping the number of claims as it would not apply to you.