I measured the seam, it is a scant 1/4 inch, and I did press it well. I would be less concerned if this only happened to one of the blocks but ALL 4 came out to the exact same measurement of 4 inches. If nothing else, I'm consistent.
My inclination is to cut down as well and I think this is another of this person's poor directions. For a nine-patch block she had us cut 4 inch blocks and told us the final block would make a 12.5 inch square (really? She's been doing some fuzzy math). I really hate it when someone is obviously using a computer program to make up these things but doesn't take the time (or knows less than I do and this started out being my first quilt) to get it right. Frustrating.
Sorry for the rant. I just hate wasting the hour on something that will never be right.