Ann: Bonus Issue of Shares, page-32

Those who take the view that this is a net positive action, because if the shares go up they now have more shares that benefit, are missing one thing: any increase in the value of PET will now be shared with more shares than before, so the per share increase in value will decrease slightly compared to when there were less shares outstanding. So the net result is that you end up enjoying the same increase in value either way.

The analogy I'd use with all share splits, bonus issues, etc is this:
Let's say I have a pizza. I cut it in half, and give you half the pizza. You have half a pizza.
Now let's say I take another pizza, cut it in quarters this time, and give you 2 pieces instead. You still have half the pizza.
Even though I may tell you you've got 2 pieces instead of 1 this time, the amount of pizza you have does not change.
Maybe someone else can explain it more elegantly, but I hope I've captured the gist of it here.