Hi. I hope so that I will able to express my thought. I think that means that "I will check again to be certain that something is done" or "You should remember that you need to do something". For another example: 1, "Before you leave, make sure you took your wallet" it's mean that before you leave a place you have to check where is your wallet, you need to be certain that you took it". 2. Make sure to water the plants on Monday". It's mean that you need to remember about doing the acitivity. You can't forget that is important.