Here is the square that was hidden within last week's magic square:
Look at the bottom right corner in the picture below. You can see half of the hidden square, outlined in green:
The final step is to make a magic square out of four of the hidden squares. The stitch counts are all contained in the first magic square, so no new calculations need to be made. However, it will take somewhere between 12 and 15 hours to tat. More on that in the next week or two.