fig = figure('position',[100 100 850 600]);
fig is created with a particular fixed size and position.
for p=1:len
and multiple times,
myMovie(p)=getframe(gcf);
it is captured,
closereq
and right after the figure is captured, it is deleted.
Then the next iteration of the loop is started, and has plotting commands, so a new figure is created automatically. But the automatically created figure has the default figure size and position, not the hard-coded [100 100 850 600] size and position. So when you capture it, it is not going to be the same size as the figure from the first iteration.
