Start by drawing a red circle on EVERY square.
Then add a variable that counts (and keeps track of!) how many circles you HAVE drawn.
Then add a conditional statement that draws a circle only if you haven’t drawn enough circles.
Part of you final code will look something like this:
// Maybe draw a circle?
if( num_circles < ??? ){
fill( ???, ???, ??? );
ellipse( ???, ???, ???, ??? );
num_circles += ???;
}