GMAT Strategy

I haven't used Kaplan's materials myself, so I can't really comment on your results on their test - perhaps others in the community have and can contribute. We've found our tests to be fairly representative for the most part, although there are always some people who have very different scores (higher and lower) on the real test.

Given your score improvement, you seem like you've been doing the right things already! Your best improvement, especially at the highest levels, will come from analyzing the practice questions after you do them - what was the basic principle being tested? What words in the problem allowed me to recognize that? How will I recognize another problem in the future that's trying to test the same principle? Did I do this problem in the best way? If not, how will I do it again next time? Why are the wrong answers wrong? What are the traps built into the question? Etc.

Make sure you're doing lots of thoughtful analysis about every question you do - don't just do lots of questions without this analysis or it will be very hard to continue to improve.

Also, FYI, after you finish your 6th test, you will continue to get new tests but you may start to see some questions you've already seen. The "6 tests" thing just means that you are guaranteed not to get any repeated questions during the first 6 tests.

Good luck!