are you trying to copy the file to the EERM container, or the stick itself? Remember you need to copy files to the container, not the stick.
Call your IT department - they should be able to help you with this.
I'm using the managed part, not the stick itself.
And since my boss left (and he took all the McAfee knowledge with him) _I am_ the IT department.
So, a bit more help would be appreciated.
Container of size equal to the size of the device is created. Once you have authenticate the container gets unlocked and you can now copy data on to the container. Hence free space shown before and after authentication is different.
What version of EEFF was the USB stick initialized with ? Are you trying to copy the 2.5 GB file to the USB stick on an offsite machine (machine without EEFF installed) ?
The issue looks similar to https://kc.mcafee.com/corporate/index?page=content&id=KB76741, this was resolved in EEFF 3.2.9
Hope this helps..