The easiest way to get it correct is to slightly over fill and then suction off the excess with a measured lenght of suction tube. The listed amounts are provided to get you close. I recall Fre slightly overfilling in his video series and then using a home made jig to suction the level down to his target level. The amount will vary by brand of spring you use too and the fork tube oil levelshould be provided by the after market spring maker.
Volume is NOT the way to refill the forks unless they are completely DRY, to include the inside of the cartridge. If you are changing the oil, you CANNOT fill them by volume, or you will have WAY too much oil in the forks and they will not have their full stroke, and can blow the seals.
Be sure to fill by level... fork collapsed, spring out.