Aliens Invasion Health Bug (Android Game)

Today I was playing a game called Aliens Invasion on my android device on my way to work.

In the game you are cowboy  and you have kill the aliens of each level, the more you kill the more money you get. Money can be spent at the end of the level on  new weapons, ammunition, health and lives as shown in the following figure.

I just realized that if you start a new level, quit the game and start again the game and resume it your health level will be increased to 100%. In the beginning I thought it wasn't a bug but a feature, but I realized that it wouldn't make sense to sell health packages. In the following figures I show two screen shots before and after quitting the game:

As nobody can be harmed, I published this just after reporting it to the development team so it still works.