What you are seeing is absolutely no different than what you would see with regard to a computer hard drive. You buy a 500 GB hard drive machine and I assure you that right out of the box if you check the available storage capacity - it will be 40 - 50 GB less than the advertised 500 GB storage capacity.
The OS and preinstalled apps that come on any computer already account for a portion of that storage space.
I happened to be browsing the internet tubes, and stumbled upon this thread. I'm afraid your answers aren't exactly accurate.
This "missing space" is not being taken up by the OS or whatever. iOS is what accounts for part of that orange "other" space and it is actually contributing to your used space. That "missing" 2GB is a simple explanation of math and measurements. The problem is that there are two different measurement standards for Gigabytes: decimal and binary. Decimal measures a GB as a literal billion bytes (1,000,000,000). That is what is in your iPhone. (16GB=16,000,000,000/32BG=32,000,000,000).
Now, binary doesn't measure it that way. Binary measures in 1024 (1KB=1024bytes/1MB=1024KB/1GB=1024MB). It should be noted that both standards recognize there are 8 bits per byte. While your iPhone does include 16GB, it's being judged by the decimal standard. However, your iPhone's software measures by the binary standard. Do the math, starting with 16,000,000,000 bytes, and you divide by 1024 three times, you get your binary standard: 14.9GB. The 32,000,000,000 breaks down to 29.8GB.
That being said, you can actually "lose" an insignificant portion of that space to metadata.
It's all a bunch of marketing strategy, to be honest. It's just easier to say 16GB/32GB than to say the tedious number that it breaks down to in binary. Just like when you're buying internet service. They don't measure it in MB(megabytes)/second download speeds, because it looks too slow and the scale is too large. That's why they sell you your Mb(megabit)/second speed. When you think your 15mbps internet is SOOO fast, you're really only getting a peak of 1.875MBps. Make sense? I hope your mind can finally be at east that your phone is working just fine. Lol
Still doesn't explain why the iPhone has a difference of "4 GB" between actual and advertised (32GB) capacity, while a mac book air has a difference of (only) "6GB" on an advertised size of 256GB... the smaller drive, the larger the difference between marketing and actual Giga Bytes?
Also, it would be really weird if Disk Utility with capacity would mean "all left over disk space after you install Mac OS X".
Actually for a Macbook Air with a 256GB advertised space, it should be reporting 238GB of actual space.
There's no way it will be reporting 250GB flat unless the drive is actually 268GB in advertised size.
For any device with hard drive space, the difference is how the space is measured that's all.
Advertised space takes 1GB to mean exactly 1000 MB. 1 MB to be exactly 1000KB and 1KB to be exactly 1000Bytes.
While actual storage space is measured in increments of 1024 rather rather than 1000.
Is completely possible though awkward that Apple is using a 268GB drive in the top level Macbook Air, and is advertising it as 256GB for whatever reason.