Just my opinion here...
For the length - the directions for part 7 do say 33.5 - but if you count how many squares go down the side - there are 20 - so if they are 1.5" finished that would make it 30.5" long.
The across measurement - following the same logic would be 27.5"
Hope this helps.
EDITED BY CHOOKY Anni read this post and said what Susan has said is correct. WELL SAID SUSAN
(that means if I am wrong I am sorry but "all care - no responsibility"!!!)