To help protect against fraud, Chase sends us "tokenized" (virtual) account numbers in place of the user's true account numbers for our Auth product. The routing number is a valid Chase routing number, but it may differ from the one the user knows, and it must be used together with the tokenized account number. Chase maps those virtual numbers to the actual numbers, so they work the same for ACH transactions. There's no discernible relationship between account masks and the tokenized numbers, so you'll likely never see a match between them. In other words, always present to your customers the account number mask, not the tokenized numbers from the /auth/get numbers object.
For more information on these tokenized numbers, please refer to Chase's FAQ or the Tokenized Account Numbers section of the Plaid docs.