When you submit your primary application to AMCAS, it all has to be verified. One of the parts of the primary app is entering in all of your courses and the grades you received. When you send in your transcript they are going to check what you put in to what your transcript says and change anything if necessary. They will also change a course if you classified it somewhere incorrectly. For example if you put your intro to psychology course under "biology" so that you could sneakily boost your sGPA, they will change it to its appropriate category. Verification can take anywhere from one day (if you submit literally on one of the first days available, which is early june) or several weeks (up to maybe 4-6??). The longer you wait to submit, the longer you will have to wait to be verified. Your app will not be sent to the schools until it is verified so obiously the less time they take to verify the faster schools will start reading your file. Since most schools are rolling admissions, that is why the one thing EVERYONE says is submit your app as early as possible. Good luck!