It looks like your concern is how it is represented in the Alexa app. As far as I can see, it is showing you the right information being 0% = open and I will assume 100% = closed. It is certainly not intuitive to see it that way but keep in mind that on the Alexa side, it only keep track of percent number.
You could use a proxy Rollershutter item if you are keen in having it represented the other way.
Also, if you want to have UP, DOWN and STOP buttons modeled in Alexa, you could use the example below.