GMAT scores are based not simply on how many questions you answer correctly but on the difficulty levels of the questions you answer correctly.
So, what's likely happened is that, while you got more questions correct on your most recent test than you got correct on your previous test, the difficulty levels of the questions you got correct on your most recent test were not as high as the difficulty levels of the questions you got correct on your previous test.
Seeing relatively high difficulty questions takes getting getting questions correct in relatively long strings. So, what you will likely see if you compare your two tests is that you got questions correct in relatively long strings more on the first test than you did on the second one.
If not, then there was some other factor in the pattern of how you answered correctly and incorrectly that resulted in your being at lower difficulty levels on the second test.