Smaller disk size after erasing of data

[Khakpour]

Hi there

I wanted to make a Boot Camp-partition on my MacBook Pro (250 GB). The reason is, that the university I attend only use Windows-programs. I started The Boot Camp-assistent, and chose a 200/50GB partitioning. After a few minutes the partitioning resulted in an error, stating that the program couldn't move certain files. After a quick google-research I found that I had to backup and erase the disc (Macintosh HD) and make a new partition and re-install OS X on it.
But having done that, I went to the Boot Camp-assistent again, only to realize that the disc size now is only 227 GB!

My question is: How come has the disc size decreased and how do i get back to a 250 GB?

I really hope, that someone can help me, cause I'm quite useless when it comes to computers.

 

[simsaladimbamba]

How did you do a clean install of Mac OS X?
What does Disk Utility say and show?

 

[Khakpour]

I took a complete backup using Time Machine.
Opened Disc Utility - Erase
Format: Mac OS extended (journaled)
Name: Macintosh HD
and clicked Delete.

Thereafter I re-installed OS X.

 

[simsaladimbamba]

I took a complete backup using Time Machine.
Opened Disc Utility - Erase
Format: Mac OS extended (journaled)
Name: Macintosh HD
and clicked Delete.

Thereafter I re-installed OS X.

Then the size should be okay, so what does Disk Utility say?

 

[Khakpour]

Then the size should be okay, so what does Disk Utility say?

It says:

Size: 249,72 GB
Free space: 228,52 GB

But when I used Boot Camp the first time, I had 250 GB at my disposal.
Now it only says 227 GB.