Help me understand Time Machine...huge file size

I recently activated Time Machine to save on a NAS.

It ran last night at 7 pm and saved approximately 32 GB. I thought it was excessive considering that I had not made many changes since the last save.

This morning it is again saving 32 GB. I have added a few albums to my iTunes folder, but this is on my NAS itself and not on my Macbook Pro. I have not done anything else.

So, it is normal that Time Machine is saving 32 GB 14 hours after the last save in which the computer was shutdown?

Yes, because it's creating a new back up of everything each time, so I assume that you have around 32 GB of HD space in use on the computer you are backing up.
It only saves the small changes on it's hourly incremental back ups, so if you shut down the next back up will be a full one.
If you look at your time machine back ups, you should be able to see how big each one is.

Thanks for clarifying that.

I have used about 230 GB on my internal hard drive and have no exceptions selected in my Time Machine preferences, so I don't know where the 30 GB comes from.

However, now I understand how it works.

Thanks.

No problem. That is a little odd mind you. Let me look into that a little more for you.

Edit. I think, and may be wrong, but that additional space is for the hourly incremental back ups that it runs. That would appear to be the most likely.
I never switch my Mac off, so TM runs every hour and I never look at how much data it's transferring. It took 4 months before it started deleting data from old back ups (on a 1.5TB HD).