From the Super Mario Wiki
10-Point Star is a collectible item that the Yoshis can use in Super Mario World 2: Yoshi's Island, and its remake, Yoshi's Island: Super Mario Advance 3. It can be obtained by winning certain minigames. It is worth 10 Stars and can raise the Yoshi's Stars (giving him 10 more seconds for the Countdown Timer). There is also a similar version of a 10-Point Star called a 20-Point Star.