Its still there...
In order to know where the 3 Gb went, you have to understand how hard drive manufactures label drives and what the capacity of a drive is.
The underlaying achitecture of storage states that there are 8 bits of data in 1 byte of data. Also there are 1024 bytes of data in one kilobyte of data. There are 1024 KB of data in 1 MB of data, 1024 MB of data in 1 GB of data, 1024 GB of in 1 terabyte (TB) of data, Ad nauseam.
You may ask, what is the difference between lowercase b (b) and an uppercase b (B). (b) = bit, (B) = byte. (8b = 1B)
NOTE: Kb and KB are NOT THE SAME THING!!!
So, now we are ready to do some math. Harddrive manufactures label drives as (for our example) 60 GB. WOW! a whopping 60 GB, but, as you will soon find, they are decieving you on a mere technicality. (notice they never say 60GB of DATA...)
Data structure overhead is where the extra 24 bytes of data come from. (1024 instead of an even 1000)
60 GB = 60,000,000,000 bytes of data. (according to their specifications)
60,000,000,000 bytes = 58,593,750 KB of data
58,593,750 KB = 57,220.5 MB of data
57,220.5 MB = 55.8794 GB of data.
So, to answer your question, you never really had 60 GB (if you did, the drive would be labeled as a 64.42 GB drive.) So, don't worry, at least you didn't get a 200 GB drive, and wonder where 14.7 GB of data went....