39*10*8 minecraft turtle block break

turtle.refuel()
for b = 1,8 do
    for i=1,5 do
        for w=1,39 do
            turtle.dig()
            turtle.forward()
        end
        turtle.turnRight()
        turtle.forward()
        turtle.turnRight()
        for r=1,39 do
            turtle.dig()
            turtle.forward()
        end
        turtle.turnLeft()
        turtle.forward()
        turtle.turnLeft()
    end
    turtle.digDown()
    turtle.down()
    turtle.turnLeft()
    for i = 1,10 do
        turtle.forward()
    end
    turtle.turnRight()
end