It easy, its just a table to set the amount of experienced gained after killing a creep.
Level one gives you 80% of the experience for killing a creep.
Level two gives you 70% of the experience for killing a creep.
and so on.
Now you see that the fifth number is 0, so at level 5 you will gain 0% of the experience for killing a creep.
you need to increase that in order to still receive experience, you can add more numbers for more levels off course.
I always personally remove the 0, that will just make the table do the rest for me ^_^