Remember that’s just basic tech training which will put him at a number 3 skill level, meaning he’ll enter tech school with an MOS skill level of 1 - a helper.
He’ll graduate tech school and become a level 3 - an apprentice.
Then he will go to his PDS and undergo a period of OJT (on the job training) where he will progress from a 3/apprentice to a 5 level journeyman.
As a 5/journeyman he will work in his field until eventually becoming a 7/craftsman, and if he stays in long enough and becomes an advanced expert in his field he may finally end up a 9 level or even 10 level (a superintendent or chief) in his field, which is kinda like a military equivalent of getting a Doctorate.
3 level is kinda like having an Associates degree, 5 level is kinda like a Bachelors, 7 level is kinda like a Masters, and 9/10 is like a Doctorate.
To get a 9 or 10 level though he would have to progress to the rank of E-8/Master Sergeant (9 level) or E-9/Master Gunnery Sergeant or Sergeant Major (10 level, and E-9 is the highest grade possible for Enlisted Marines). The vast majority of Enlisted Military members make it to 5 or 7 level - only a select few make it to 9 or 10.