Did you press and hold the set button first sir? In case that your unit isn't working we can recommend you to our service center so they can check your freezer. You may call to our hotline 8230-1555 local 8300 - 8314
Yes you are correct -40 is colder than the -7.. In mathematics, usage of - sign means lower value even though the we have higher number after the - sign..
Yes sir, You may also request a soft copy of the manual For urgent concerns, you may contact us at our service hotline: (02) 8230-1555 local 8300-8314 / 0917-8696111 / 0925-7372477.