This requires a little math, but it will always depend on the number of characters you have already unlocked on Zooba.

If you divide them by 5 and disregard the decimals, you will get the exact number of runs.

For example: If you have 16 Characters: 16 divided by 5 equals 3.2. This means that your toolbox will run 3 times!
If you have 7, then it will run only once because 7 divided by 5 is 1,4.

You can learn more about earning items by tapping here.

See you at the Zoo!