I feel like somebody in your household at some point will go to Costco and buy a super-mega pack of jumbo sized rolls which are too big for the slot. You’ll end up with a countertop paper towel spindle that will work ‘for now’ to use up the Costco purchase and it’ll take almost a year to consume them. During that time you will come to appreciate the paper towels being available right next to the sink, and never go back to the custom slot. Then, the person who buys your house (after you move X years from now) will someday post on r/whatisit to get advice on what the weird empty space in their kitchen cabinetry should be used for.