From Webkinz Insider Wiki
Operation Gumball is a Webkinz World Arcade game.
The object of Operation Gumball is to guess the hidden number of gumballs by entering digits with your keypad. You get one green ball for every number that is in the solution and in the correct place, and one red ball for every number that is just out of place. You get no balls for numbers that are not in the actual number.
Use the keypad to enter the numbers.
You could start off by making your first guess 123. If nothing comes up, continue the sequence, by going 456, then 789. By now, you should have a pretty good start in only three guesses. You go from there!
According to the the WI High Score Board, the highest score achieved by a WebkinzInsider member in Operation Gumball is 124,273 by member cocoabean.