the single quote separators are there to add spaces between the values.
think of it this way:
[Name] = Test Product
[ID] = 123
[color] = Blue
[size] = small
and you have the full description set to:
[Quantity] . ' ' . [Name] . ' (' . [ID] . ')' . ' ' . [color] . ' ' . [size]
that will result in the following output:
1 Test Product (123) Blue small
the order doesn't matter.