This is actually correct (If I understand you are pointing out I used a double z instead of a single z).  The code has always done a String.format on the resolution property (see XYZMapReader.java:95) that actually was my inspiration for this patch (I had code that didn't want the double padding, and felt it should be controllable.  In the past I just did an inline over-ride, but that is no fun to maintain on my own branch...).