Your documentation is referring to the linux version of fdisk which you run after you boot your gentoo installation cd here is an example taken from one of my hard drives:
Disk /dev/hda: 240 heads, 63 sectors, 1323 cylinders
Units = cylinders of 15120 * 512 bytes
Device Boot Start End Blocks Id System
/dev/hda1 * 1 610 4611568+ 7 HPFS/NTFS
/dev/hda2 611 1287 5118120 83 Linux
/dev/hda3 1288 1323 272160 82 Linux swap
See type 82 is Linux swap and 83 is Linux partitions respectively, which while in fdisk you will set the type, /dev/hda refers to my first hard drive if you have a removable it is usually referrred as /dev/sda. I hope this isn't confusing you more, good choice on gentoo I also am going to give it a go tonight