Also, a bunch of people have asked this during my time at primary, so I am posting here.
With the MIF system, your NSS is a function of your aggregate score and your cumulative unsats/marginals with respect to the averages of your squadron.
Your overall aggregate score is unavailable in TIMS as far as I know. You're able to see the stage score totals for the cumulative score in each stage. For those of you who don't know what the score actually is, it is simply the ratio of your cumulative graded totals to the MIF for each corresponding maneuver completed. Thus, if you had completed one maneuver, ie. Landing Flap Landing and received a 5, where MIF is a 4, your score would be a 1.25 (5/4.)
So,[for the T-6b students] in TIMS you can see your overall ratio in Contacts, Formation, Radio Instruments, Basic Instruments, and Navigation. Many people mistakenly believe that these overall scores are all incorporated evenly. Others believe that these are weighted differently. Neither is true, because the stage scores are not used. In actuality, Contacts "counts more" than Navigation for example, simply because you will have more graded maneuvers in contacts. Every maneuver in every stage counts equally. Thus, your overall score is the sum of every maneuver you've completed in every stage divided by the MIF for every maneuver.
Your overall score will be something like, 1.1713 or 1.1556. This score is then plugged into the formula given in the JPPT. Essentially, the squadron average score is subtracted from your score. The result is divided by the standard deviation. That result is then multiplied by .9. The same thing is done with your unsats/marginals and the result is multiplied by .1. The two figures are added and the sum is multiplied by 10 and added to 50. This result is your "phase aggregate score."
The PAS is then normalized by the same process. The squadron average PAS is subtracted from your PAS and divided by the squadron standard deviation of PAS. That result is multiplied by 10 and added to 50 to produce your NSS.