eText Template - SUBSTR not working

Hi,

I am struggling with below SUBSTR function not working to display the right 10 numbers. If I run the below function in SQL Plus, I get the correct right 10 numbers.

SUBSTR(TRIM(TO_CHAR(SUM(TO_NUMBER(SUBSTR(OutboundPayment/PayeeBankAccount/BankAccountNumber,1,15))))),-10)

I also tried the below way but no luck

SUBSTR(TRIM(TO_CHAR(SUM(TO_NUMBER(SUBSTR(OutboundPayment/PayeeBankAccount/BankAccountNumber,1,15))))),-10,10)

However if I do something like get only the first 5 numbers like below, it works.

SUBSTR(TRIM(TO_CHAR(SUM(TO_NUMBER(SUBSTR(OutboundPayment/PayeeBankAccount/BankAccountNumber,1,15))))),1,5)

Appreciate your help.

Thanks.