The scaling of the last instruction bothered me for a while too. Taken literally the instruction will permit circles of any size around the dot.
The artwork though gives the answer. The circle should cut the bottom of the grid at its centre and meet both the left and right top corners of the grid. This takes the final circle outside the usual section of the page that we are requested to include in our submissions.
For this reason I have decided to submit the whole page rather than the usual cut out grid.