Default [Q] Android Official Updating

Hey guys,
I just wanted to know one thing about Android official updating. When i update Android e.g. from ICS 4.0.4 to Jelly Bean 4.3(Jelly Bean 4.3 update for Samsung S3 GT-i9300 is about 950MB) does that lower my current storage(by current storage i mean storage that i have on ICS) permanently by those 950MB?
I mean if it lowers my storage like that, after a few updates i wont even have free space for anything else
Im sorry if my english is bad, and if you didnt understand something, please ask.
Oh and btw i have Samsung S3 GT-i9300 if that means anything to you
Thanks in advance,
Slim Shady