I don't follow why items at the beginning of the table would have a higher probability of dropping ?
If we assume the random number is truly random, then the probability of an item is in proportion to it's chance value versus the sum of the chance values of all the possible items, i.e.
Item 0 has a 5/65 chance, item 1 has a 10/65 chance, and item 2 has a 50/65 chance.
The position in the table should have no bearing on it's chance to be selected, unless there is something I am missing. I didn't write this code BTW, this is just my conclusion by looking at it.
EDIT: I took too long writing this before you edited your post
