Bank Reconciliation Tool and Bank Statement V13

Anyone knows where are the account opening balance and the closing balance values comes from? See the screenshot below.

Also, if anyone can explain where and what are the values on the bank Reconciliation Statement? See the screenshot below.

I can’t find an explanation on the ERPNEXT documentation or from other discussion on this.

Anyone can help me with this? Willing to pay for consultation fee to understand the reports. Thank you.