lemme clarify - there aren't any "marks" on the fork for this - you have to measure it.

A tool like the motion pro oil gauge allows you to make this adjustment easily- you measure the tube below the ring to the correct length, then fill the fork to the ballpark, and suck out the excess through the tube with the syringe.

I built my own for about $5 worth of parts from the local hardware and vet supply stores:

 

So I could take micrometer or something similiar and measure and just measure from the top of the fork? I could make something similiar without the slide.

 

Thanks again for the advice everyone. I went ahead and swapped out the seals and oil this weekend. Everything went smooth and the bike feels worlds better now.

 

Sweet! It's a good feeling when you learn new things. Makes doing all the other
parts of motorcycle maintenance less intimidating, too.
Grats! Ern