unable to capture tithing on my account

Hi,i m unable to capture tithing on my account,i m using savings account not checking account,why is the system asking me for a routing number

The bank account must include both the routing number for the bank and the savings account. The message asking for the routing number most likely means the number you provided does not work. Some banks use different routing numbers for different types of transactions. Contact your bank to find out what the routing number is for your savings account using electronic funds transfers (EFT). The online donations system uses electronic funds transfers to make the transactions.