Hi Malolo355,
Practice CATs are great tools to use to measure your ability level, but they can be more or less accurate depending on how seriously you treat the experience. Here are some thing to consider:
1) Did you take the ENTIRE CAT (or did you skip the Essay and/or IR)?
2) Did you take the CAT in a realistic way (did you pause the Test, listen to music while taking it, eat/drink while taking it, etc.)?
3) Did the "details" of the CAT match the details of your Official GMAT (time of day, day of week, desktop computer, taken away from home, etc.)?
The more closely your CAT meets the standards of Test Day, the more likely the results are to being realistic.
I'd say there's a strong chance that you can score 600+ on Test Day, as long as you put in the necessary work during the Exam. The GMAT is remarkably good at giving you the score that you EARN, so make sure that you earn it.
GMAT assassins aren't born, they're made,
Rich