Menu_small.Opacity will give you the value of the current opacity of the object Menu_small..
Adding a dot behind it does nothing..
I guess what you are trying to do is
every tick set menu_small opacity to: lerp(Menu_small.opacity,100,0.2)
so the first value is the current opacity, the second value is the number you want to get to and 0.2 is the amount it will shift between the two..
This works because every tick the current opacity is changed to a number closer to 100..
so tick 1 Menu_small.opacity = 0
lerp(Menu_small.opacity,100,0.2) value is 0+(100-0)*0.2= 20
so tick 2 Menu_small.opacity = 20
lerp(Menu_small.opacity,100,0.2) value is 20+(100-20)*0.2= 36
so tick 3 Menu_small.opacity = 36
lerp(Menu_small.opacity,100,0.2) value is 36+(100-36)*0.2= 48.8
so tick 4 Menu_small.opacity = 48.8
lerp(Menu_small.opacity,100,0.2) value is 48.8+(100-48,8)*0.2= 59.04
etcetera..