First Time Machine backup calculated at more the the actual amount?

[iamMacPerson]

I upgraded my moms laptop to have dual drives (1 SSD in the standard bay, 1 HDD in the ODD bay). Well, due to that I had to restart the backup. But now there is a new problem. Total, the HDD and SSD together make 740 GB, however only 267 GB is used. TM, however, see that it needs to backup 284 GB, which isn't true. Plus, that 267 GB includes the system folder, which TM shouldn't back up, so in threoy the backup should be smaller then what the HDD and SSD use. I have tried a PRAM reset and SMC reset, didn't work.

Is this normal? I have never seen it happen before and I have used TM for years.

Machine is a 2010 13" MBP running 10.9.2.

 

[h9826790]

Time machine will backup the system folder. And this is one of it's main purpose and function.

I know it doesn't make any sense, but 284 vs 267 is not much different. May be Mavericks use different format for time machine to store data and it increase the size a bit.

I will say no need to care about that. Your backup disk should be far bigger than 750G anyway. I use time machine for many years as well. I could never understand it's mechanism (e.g. Large amont of data backup shows up in a normal hourly backup but I didn't do anything large to my computer within that hour, and time machine can finish it quickly without reduce the space remaining in the time capsule)

All I know is time machine is very reliable. Easy to recover my data. And you can never figure out how it backup your Mac