It goes on to add:use 4.41 inches or 112.0 mm IF the fork is disassembled. It also states to use these figures if the fork is left in the frame( not disassembled). I ride an '08 FLSTN and my H-D workshop manual states for '08 FLST FLSTN & FLSTC the forks take 13.4 fluid ounces or 395 cc's. You can go up or down in 1/8" measures to tune the front end to the way you like the feel. The spec in the book is a starting point.
You also need to have the tubes compressed all the way in the forks (see the pdf below). If your caps do not have a fill port in the center, you have to do this with the caps off (be careful when you unscrew these so the springs don't launch the caps to the moon!) and the springs out of the tubes. But I use a piece of clear plastic tubing marked with the air gap, and my trusty mini-vac vacuum pump to draw off the excess. There are tools you can buy to do this with an adjustable ring on a thick needle (SS tube) that you can set to the air gap and then siphon off the excess to get the desired air gap. Regardless of whether you are renewing the oil or filling from "dry", the key is to add (or draw out) enough oil to leave a specific "air gap" above the oil level in each side to +/- 1/8".
If "dry", then add the amount shown in the book and then do as below. If you are just changing the oil, the best idea is to measure how much oil you drain from each side, and start with that much on the make-up.
Click to expand.The exact amount of fork oil you need will depend on whether you are just changing the oil or you have disassembled the forks and are filling them from "dry".