Lua CC Simple 2x2 Shaft Down

function slab()
    for i = 0, 3, 1 do
        turtle.turnRight()
        turtle.dig()
        turtle.place()
        turtle.turnLeft()
        turtle.dig()
        turtle.forward()
        turtle.turnRight()
        turtle.dig()
        turtle.place()
        turtle.turnLeft()
        turtle.turnLeft()
    end
end
function update()
    shell.run("pastebin" "get" "YhK59cm5" "blockCheck")
    shell.run("pastebin" "get" "2EkpdDpX" "fuelCheck")
end
function clearCurs()
    term.clear()
    term.setCursorPos(1,1)
end
function doubleCheck()
    shell.run("blockCheck")
    shell.run("fuelCheck")
    turtle.select(1)
end
update()
clearCurs()
print("How deep do you want the shaft to be?")
y = tonumber(read())
clearCurs()
print("Depth goal: "..y)
tbu = 0
for i = 1, 16, 1 do
    turtle.select(i)
    if turtle.compareTo(1) then
        tbu = tbu + turtle.getItemCount()
    end
end
print("Total amount of usable blocks: "..tbu)
print("Maximum amount of blocks to be used: "..(8*y)+4)
print("Calculated amount of fuel to be used: "..((y*5)+(y-1)))
sleep(1)
f = turtle.getFuelLevel()
doubleCheck()
for i = 1, y, 1 do
    turtle.digDown()
    turtle.down()
    slab()
    if (i % 3 == 0) then
        doubleCheck()
    end
    term.clear()
    print("Depth goal: "..y)
    print("Remaining: "..(y - (i-1)))
end
for i = 0, 3, 1 do
    turtle.forward()
    turtle.digDown()
    turtle.placeDown()
    turtle.turnLeft()
end
for i = 1, y, 1 do
    while turtle.detectUp() do
        turtle.digUp()
        sleep(1.5)
    end
    turtle.up()
end
turtle.turnRight()
turtle.turnRight()
turtle.placeDown()
for i = 1, 16, 1 do
    turtle.select(i)
    turtle.drop()
end
l = turtle.getFuelLevel()
tfu = f - l
print("Total fuel used: "..tfu)
print("Total fuel left: "..l)