Jay is correct, the "Study Verify" checks to make sure the number is not larger than 9 9's. There is a way to bypass that check. Put the number in SSI Script -- for instance, for the maximum value enter [%999999999999%] to allow 12 digits. The verifier won't make the check if it encounters SSI Script.
However, let me add a HUGE WARNING and disclaimer: There is a reason for the built-in limit of 9 digits. The system isn't designed to handle extremely large numbers with precision. When I tested 16 digits, it was rounding both the answer I typed in as a respondent and the range that was displayed in the error message when I typed in more than 16 digits. Additionally, during export there will likely be additional rounding or number overflow issues. Numbers from -2,147,483,648 to 2,147,483,647 should be fine (the range of an integer type), but outside of this range you'll run into trouble. If you choose to bypass the built-in checks, be sure to test thoroughly both data collection and export / analysis. Additionally, you may see different behavior between version 7 and version 8.
The safe way to store an extremely large number is to store it as text.
