Hi @Seller_0aKQxocDWQhti,

Taking a look at other sock listings, it appears your should be able to enter that size or similar. This help page might be useful.

"What if my product size is not an option or falls under an additional attribute?

First, verify that you have selected accurate values for Target Gender, Age Range Description, and Size Class attributes as these will determine the values available under subsequent attributes. To provide additional sizing information consider using sizing charts to give customers more context around product-specific sizing. If you feel that you have a valid use-case where your size isn’t an available option, you can submit a request to Amazon Selling Partner Support. Amazon will process and consider your request; however, certain requests such as submitting a request to add 28 UK to the US list of valid values will not be acceptable."

For your second question, I found this page that might be relevant. It's about footwear, but talks about a "footwear to size" attribute. The Apparel size standards talk about something similar.

"Footwear To Size [Conditionally Mandatory]: Select the ending shoe range value. This will be concatenated with the previous Footwear Size selection to build a range. For example, if you want to list a product as 8-9, you would select Footwear Size value as 8 and Footwear To Size value as 9. Amazon will concatenate these values as 8-9.

Examples: 8-9, Small-Medium, 3-6 Months

Notes:

This selection becomes required when Footwear Size Class is equal to Numeric Range, Alpha Range, or Age Range.

Populate this field only if you are listing a product with a shoe size range.

The value selected in Footwear To Size must be greater than the value selected in Footwear Size. For example, we will allow 10-11 (where 10 was selected as the Footwear Size and 11 was selected as the Footwear To Size). We will reject values such as 6-5 (where 6 was selected as the Footwear Size and 5 was selected as the Footwear To Size)."

I know that was a lot of info. If you still have questions, feel free to reach out to Seller Support or post again!