I don't know I'd say any way is a correct way or one that will get you right on all the time. I prefer to use the Wingspan divided by 2.5 for most shooters. This doesn't always get it right on, but it gets in the ballpark, as most other methods do.

Then I suggest to shop for and buy bows that are adjustable for drawlength by either replaceable modules or a rotating module. Very seldom will a new shooter get the correct draw length and most people shooting for years still don't get it right.

Those who shoot target or are dedicated to some form of archery and experiment find that they can vary a little from bow to bow dependent on bow design. Correct draw length is not always a specific measurement taken with a tape or other means. It's found by shooting a bow and finding out just at what setting a bow holds and aims the best. This might mean twisting strings and such, making changes of 1/4" or less. Using this criteria takes time. Sometimes years, and it's usually a lot shorter than people want to shoot.