Hey Triforce,
Thank you for your reply! In fact the score is supposed to grow from a small size to a bigger size. I also use fade behavior, so it fade in, start to grow and the second after, it fade out... doing so for each point. The fade is ok, the problem is with the sine's size movement (including width and height).
I still can do this with every tick/seconds-> set size...etc, but i thought that may be i'm missing something with the sprite font object or with the sine behavior...