OS X requires a certain amount of free space on the startup volume for its own use. Two things you need to know before going any further:ġ.
If the partition is using 168 GB of a 240 GB partition, then 72 GB are free, but that does not mean they are all at the end of the partition (as I explained in my first post). Free space & used space on a partition, & its total capacity are entirely different things.
If the OS X partition is 240 GB & the drive's capacity is 250 GB, then there is only 10 GB left for the Boot Camp partition - period.
