Hi Nasthor,
Practice CAT scores are only as realistic as YOU make the process of taking the CAT. The more the 'CAT-taking event' deviates from what you'll face on Test Day, the more likely the score is to be inaccurate (and in most cases, that means "inflated").
Here are some details to consider: When you took this CAT...
1) Did you take the ENTIRE CAT (including the Essay and IR sections)?
2) Did you take it at home?
3) Did you take it at the same time of day as your Official GMAT?
4) Did you do ANYTHING during this CAT that you couldn't do on Test Day (pause the CAT, listen to music, etc.)?
There are plenty of CATs on the market that are 'close enough' to the Official GMAT that their score results can be described as reasonably accurate. If you think that this score result is 'off', then it probably is - and you might want to invest in some other resources.
1) How long have you been studying?
2) What is your goal score?
3) When are you planning to take the GMAT?
GMAT assassins aren't born, they're made,
Rich