What is the minimum number of digits for a supplier bank account?

Summary:

We entered information for a supplier for them to receive payment via ACH/EFT from us. We entered their ABA routing number and bank account number as it was given to us. When I created the electronic payment file, the bank account number did not populate and instead was replaced with a repeat of the ABA routing number. 

Content (please ensure you mask any confidential information): My question is – how many digits are required for the Bank Account Number?

Version (include the version you are using, if applicable): 23D

Code Snippet (add any code snippets that support your topic, if applicable):