If you have entered any tournament results manually in your old databases then you won't get those results in a new database if you only import the hand histories. You would need to either enter the results manually or export your results from the old database and import those files.
If you have a difference in cash games and you can identify a period which doesn't match between databases we'll be happy to investigate for you, if you attach the hand history files for a session which didn't import correctly to a
Support Ticket and tell us how much you actually won or lost.