A&W should have just called it the "Quarter-plus pounder".
It's a 1/12th of a pound more.
"1/3 to 1/4 is [...] how much more", as is, is ambiguous: on some cultures, "how much more" may depend on the local field of reference (1/3), and on others on the global one (1)
That conclusion requires fraction devision which most folks can’t do in their head. The HN crowd can but it still takes some thought