Confused with Practice test results

The composite scores on your practice tests look really erratic, Nishant, but I don't think that they're quite as strange as they look. As MartyMcfly correctly mentioned, every company has a different algorithm for its practice tests, and it isn't unusual to see quite a bit of variation if you're doing a mix of GMATPrep, MGMAT, and Kaplan tests. If we look at the quant scores alone, your results seem to be within a reasonable range, and most of that variation can probably be attributed to the differences in practice tests. For many test-takers, the MGMAT quant tests feel particularly hard, and it wouldn't be unusual to score a few points lower on those.

I take the GMATPrep score far more seriously than the others, and it suggests that your quant skills are pretty solid. Keep working, but I don't think you ultimately have too much to worry about on that section.

On the verbal side, your scores are consistent, but with one outlier... and that outlier happens to be an MGMAT test. Usually, those tests are pretty good, but they can never be as accurate as your GMATPrep scores, and I frequently meet test-takers who will have an occasional, very strange-looking result on their MGMAT tests. So the bad news is that the 40 looks like an unusually good day, or a test with some unusually fortunate questions.

So focus hard on your verbal! If you can get a 40 on verbal once, you can get it again... and hopefully, it will be on the real thing next time, and you won't need any luck.

Good luck with your studies!