APP13 IPTC Decoding

Hi,

Below is an example of the APP13 part of a JPEG.

FF ED 00 2E 50 68 6F 74 6F 73 68 6F 70 20 33 2E 30 00 38 42 49 4D 04 04 00 00 00
00 00 12 1C 02 00 00

So, that is
FF ED - APP 13 marker
00 2E - APP 13 length
50 68.. 42 49 4D - Photoshop 3.0.8.BIM

My question is... what does 04 04 00 00 00 00 00 represent? I've looked on the
net quite a bit and I can't figure that part out, I know what follows it is tag
information but and I'm wondering if it relates to that.

Any help is gratefully appreciated!