Off the top of my head, the dollar amounts may be different because

• The general ledger is fiscal period based, and SalesAnalysis is using the calendar month.
• SalesAnalysis is including taxes and/or miscellaneous charges in the amounts it is reporting.
• Someone has edited and changed the amounts in the SA database.
• Someone has purged transactions in the SA database.
• There are still transactions waiting to be retrieved into Ledger or SalesAnalysis.