The account number and IFSC code that we provide to you in the Bank Transfer section of the app is a Virtual Account Number. Even though this is an ICICI bank account, this is not the typical savings account number provided by ICICI bank. Hence to add this account as a beneficiary, please select 'Other Bank' as shown in the screenshot below.
By selecting "Other Bank" you will not have the limit of 12 digits and this will get added successfully. You can then transfer via IMPS, NEFT, or RTGS once the beneficiary is added.