From your description, it is not totally clear what you are referring to. The General Ledger Summary does not list monthly balances, no matter what you mean by that phrase. Instead, for each account you have created, it lists that account’s opening balance, debits, credits, net movement, and closing balance. The opening and closing balances are as of dates specified when you first create that specific General Ledger Summary report. You can generate a report for any period of time.
The numbers at the bottom are totals of debits and credits for all accounts. Remember, in double-entry accounting, there at least two accounts involved in every transaction. So the sums should match.
This report has nothing to do with profit or loss. For that, see the Profit and Loss Statement.
If you’re not familiar with the general practices and terminology of double-entry accounting, you can learn most of what you need to know to use Manager at http://www.accountingcoach.com. You should understand that Manager is a tool for accounting, and it makes many things easier with its features. But to use it, you must have at least basic knowledge of the subject.