Never wash rice directly in the non stick rice cooking bowl thing. Do it in a sieve and mix it around with your hand or a bowl. Can take years off the cookers life. Might be the difference between 5 years and 10 and I’ve got better things to waste my money on than another rice cooker haha
You can wash it in a seperate bowl then. The reason it is said is the rice can damage the bowl if it's washed aggressively (hits the side). Over a long period of misuse it may wear down the coating, but in saying this it's $12 in Australia and you just chuck it out when the bowl is gone (normally 2-3 years with 3 times a week use)
I am puzzled that you are having to work out through guesswork the water levels because in Australia the Kmart mini rice cooker comes with an online instruction manual and also has marks in the bowl to show how much water to fill. Perhaps this is a newer model. (Btw they also say not to wash the rice in the bowl because that could spoil the non-stick bowl after a while.)
I have a question, can you just walk away from the cooker? As in, will it turn itself off in a sense? I like the idea of putting the lid on, go have a nap and not worry its burning? Cheers