You can dictate the record limit in your field browser / parameter list in your regedit area.
Before you try to use any of the information I'm about to give you, I would urge you not to attempt this unless you can back out of it without any trouble, and only if you're comfortable in regeditor.
Open a regedit session, and go to HKEY_CURRENT_USER\Software\Seagate Software\Crystal Reports\DatabaseServer
If it's not already set to decimal, check this radio button.
I haven't checked mine, so you'll need to check what your limit is set to. If it's 50, then this is your man. If not, then bail.
If the limit is 50, then increase it to 550, and hit OK. (Bear in mind that 550 is not as light on performance as 50).
Come out of the registry, and restart the machine.
A solution with less impact, and which will only affect the field in hand as opposed to the whole application, would be to create a report which just lists the 550 records.
Export the output to a txt file, and then import the txt file into your picklist.
All the best,
Naith