How do I calculate what IMGBURN calls Image Size

OK folks, glad to join you all.

I am using IMGBURN to cut a film on DVD+R and wondered if anyone knew how the Image Size was calculated.

The output from ImgBurn is below but why the difference between Size and Image Size (i.e. there’s a TOC and what else).

I 17:01:19 ImgBurn Version 2.4.4.0 started!
I 17:01:19 Microsoft Windows XP Professional (5.1, Build 2600 : Service Pack 3)
I 17:01:19 Total Physical Memory: 3,143,520 KB - Available: 2,390,408 KB
I 17:01:19 Initialising SPTI…
I 17:01:19 Searching for SCSI / ATAPI devices…
I 17:01:39 Found 1 DVD-ROM and 1 DVD±RW!
I 17:02:05 Operation Started!
I 17:02:05 Building Image Tree…
I 17:02:08 Calculating Totals…
I 17:02:08 Preparing Image…
I 17:02:08 Checking Path Length…
I 17:02:08 Contents: 8 Files, 2 Folders
I 17:02:08 Content Type: DVD Video
I 17:02:08 File System(s): ISO9660, UDF (1.02)
I 17:02:08 Volume Label: MY TEST
I 17:02:08 IFO/BUP 32K Padding: Enabled
I 17:02:08 Region Code: 1, 2, 3, 4, 5, 6, 7, 8
I 17:02:08 TV System: PAL
I 17:02:08 Size: 3,706,789,888 bytes
I 17:02:08 Sectors: 1,809,956
I 17:02:08 Image Size: 3,707,404,288 bytes
I 17:02:08 Image Sectors: 1,810,256
E 17:02:17 Operation Aborted! - Duration: 00:00:12

Be glad if someone can assist.

Regards
Philbilldick

I would imagine part of it is the lead-out being burned. In Nero (and others) you have an an option to burn shorter lead-outs if needed.