so basically by the loop means

               (start,stop,step)

for i in range(4, 10, 2):
 print(i)

so by this loop python will run like starting the loop with as start(4) and stop before 10 and increamental step as step(2)
4 start 
4+2 ,4+2+2 step
stop before 10 ,so final is 
4,6,8