I have just recently started sewing vintage again and unfortunately I am a bigger girl so all patterns are going to need to be graded up. Now I know how to do the slash and spread method, however they only tell you how to spread it from left to right. I don’t quite understand how to do the measurements to add length. How many inches or quarter inches or whatever do you need to add per size. I have looked at a dozen tutorials and no one gives you solid numbers. Thanks for your attention.