when i hit 120 i got my normal 3 SP and when i advanced to 4th job i received another 3. somehow it allowed me to add 5 to genesis and I'm level 120. it made me place the 1 point back in 3rd job however. also my merch duped about 15million mesos figured id toss this in here too so i don't get banned over some petty change.
Yeah, next time you level up, it's not going to let you add SP to 4th job skills until you've "refunded" the 3rd job SP you used for 4th job skills; i.e. you're going to have to add 2 points to 3rd job skills until you can use the last point for a 4th job skill. (There is - or used to be - a way to bypass this but I'm not going to tell you how.)