If you want to "embed" a size-chart table in your product descriptions. You will have to create this in HTML.
You could use the HTMLArea feature inbuilt into the Add Product screen in the admin console. There is a simple "insert a table" function inherent in HTMLArea.
Another way is to create your size chart table in an external HTML editor (Such as MS FrontPage), and then copy the relevant html code off that editor and "paste" it into your product description html.
A third way is to create a size chart as an IMAGE, load the image to your images folder, and then - in your product descriptions, embed a hyperlink to that image (Again, this can be done using HTMLArea).