unable to figure out the difference in Manual Transaction Matching window for the period

Hello

The difference shown is just a difference between balance received from bank in bank statement and booked (using PP1 posting type) in your cash ledger - as per payment date in cash transaction and transaction date in bank statement line.

Provided that you are always matching cash and bank statement transactions with same date, and all your cash transactions are matched - there are transactions in bank statement not matched with relevant cash book entries.

But if you matched cash transactions dated earlier or on 19/01/2022 with bank statement line dated later, you will see this difference (on reconciliation date between these two transaction dates) even if all entries are ultimately matched and there is no difference at current date. 

in your case, I would check matching of all transactions with cash date 19/01/2022 (in View Matched transactions window) verifying bank statement transaction date of matched item.