I'm not sure I understand your question and the connection of the mask to the whitelist...Currently, UDT whitelist doesn't take a subnet mask into consideration...
Thank you for responding. My concern was, we are advertising a /24 , but, our customer only wants to accept a /28 and I am wondering if the more specific /28 will cause problems. If I advertise the more specific route will it break the /24?
Advertising to whom, how?
When I see things like this I'm thinking a BGP peering announcement with an external peer, in which case you should announce what you have been allocated/assigned by your local RIR and recorded in the RADB, and you would not want to advertise a smaller block as well as the larger aggregate (a /28 is quite small for a eBGP routing table, many places would filter such a small route)
Advertising routes in BGP has nothing to do with whitelisting in UDT...
Perhaps you could explain what your customer wants to do with whitelisting?