When you play, the fruits you launch float inside a closed gate. The number at the top shows how many fruit merges you need to unlock it. 

Once you open a gate, you’ll move on to the next stage, and your score multiplier will increase. Your current fruits will float along with you, and as they travel, they might even merge a few more times. 

Each new gate requires more merges to be unlocked. It can get trickier to keep fruits from crossing the red line, but the more gates you can open, the bigger your score multiplier will be.