if i were to take 6 months off and lose 100lbs on my squat, and i came back and added 120lbs... i would consider that a 20lb. increase...
the fact that you had squatted more than when you came back was left out... it sounded like you had never squatted anything near that weight before...
it is much, much easier the second time around... im not trying to discredit you or anything, i just think a 'new' gain of that ammount isnt likely in that ammount of time, and it so happened that you had lifted weights near that ammount in the past, which you didnt mention...