Well it's weird, I post now some images here.
I was at 0 speed. I ordered 75 meters, sub went at that depth without using compressed air. At 75 meters I ordered Surface (S), sub went to surface without consuming air.. but only at surface, compressed air decreased a little bit as you can see in the 3th image. After a while it was recharged. It happened even at speed (5 kts), but once at surface the compressed air went down with minor extent. Compressed air doesn't change if I change my depth without going to surface.
1. At surface, 0 kts.
2. 75meters ordered, air doesn't change during descent.
3. Surface ordered. Only once at surface air diminished a little.
So, I don't know how to interpret it. Air should decrease as I hit S at depth. And air should decrease when I change my depth going up without surfacing, but it doesn't. So, is it a bug? is it an unfinished stuff? Is there a fix?