What is the best way to separate product sizes for two different options in payment field product list?

My form has fields for size selection Adult and Youth...when I place the order it shows that both sizes are selected....as it start as size small.

Example...Item 1 if I select a youth L the order shows as an Adult SM and Youth L. 

What's the best way to correct this issue when I have 2 size options available?

I have checked your form and I see that for Item #1 there is an option for Size (Youth) and an option for Size (Adult). This is the reason why you are seeing both options when the form is submitted. To fix the issue, you can set up your item options in your form like this:

Where "SIZE" has 5 options — S, M, L, XL, and XXXL. And "FOR" has 2 options — Adult and Youth.

Or, you can also set the Size option like this:

You may also find the guides below helpful when setting up options for your form's product list

Create-Sub-Products-Based-on-a-Product-Option

How-to-Add-Options-to-Payment-Forms

I hope this helps. If you have other questions or concerns, please feel free to contact us again anytime.