attributes for size other than small medium large

I want to specify specific size for my product. I added size to my attribute list but I don't want it to be a drop down menu with values like: small medium and large. I want to be able to post sizes like:

Size-31.5" wide
Graphic Height-29.5" - 83.35" + bleed
Graphic Width-31.5"

Does this all have to be added under description?

S, M , & L are values - Dropdown or another is defined when the option name is setup. You just need to assign your names to your values for this
https://www.zen-cart.com/tutorials/index.php?article=57

Thanks. I do not know in advance what the values will be. I woiuld like to add those values as I add products. I am sorry if I am missing the obvious.

I woiuld like to add those values as I add products.
Add the attributes vaules after you add the product and know what they are

I see that this is how it is done with color. Adding different colors as one goes. But I don't want a long list of sizes in a drop down menu. Would this be a read only setting? I tried specifying text, but that gave me an input field.

I see that this is how it is done with color. Adding different colors as one goes. But I don't want a long list of sizes in a drop down menu.
In a product there will only be those in the list that you specifically add and this can be a sub set of all the available/added options