MB Diesel gave VERY GOOD charging instructions.

The only thing I can add is that if you do have significant leak, next time you charge it, put in a can of UV dye. Run it for a week or so, then use a black light to look for the leak. In this process, use the black light on the condensation drain water to see if it is has any uv dye in it. That way you can fix the leak and do away with the problem.

You did not say how long it took for the refrigerant to leak out. If it took several years, this could be a somewhat normal condition. It is not uncommon for a system to leak a few ounces per year. If this is the case, just recharge when the time comes. If it leaks out sooner, you should find the leak and repair it.

Good luck,