Disk Utility creates partition much larger than expected

[GrassyAssAmigo]

Hi,

I'm trying to install Boot Camp on a late 2013 27" iMac (Mavericks 10.9.5, 3.5GHz Intel Core i7, 1TB Fusion, 16GB RAM).

I'm using Disk Utility to create a new 80GB partition on the internal 1TB Fusion drive (technically 1.12TB). However once Disk Utility has completed repartitioning, the partition ends up being around 200GB in size.

I've tried creating it as FAT, ExFAT and Mac OS Extended (Journaled) but in every case the final partition ends up being much larger than expected.

The iMac is brand new, first switched on last night. FileVault is not enabled. I've previously installed Boot Camp on another iMac with 1TB Fusion drive and I didn't have this problem then. I'm using Disk Utility version 13.

Any ideas?

 

[stapoz]

When you select your disk (in Disk Utility) and then select the "partition" tab - you can't decrease the partition size?

 

[GrassyAssAmigo]

Nope, if I drag it down to 80GB and hit Apply, Disk Utility goes through repartitioning and ends up at 200GB again.

It's never exactly 200GB but it's always around that size, typically 201~205GB.