MILKE Indeed, there is a bug in application which shows its presence in a very rare situations. It's related to calculating the size of the archived file which consist of both entities: data fork and resource fork/HFS metadata. The cause of an error is mistake in conversion between different data types and, as mentioned, influences size calculations only with very specific combination of values. ende42 was that "lucky" to encounter such a combination.
I'll release the fix for this bug very soon. Unfortunately, it prevented ende42 to fully test-run the application. The contextual menu plug-in is not affected though.
(Version 1.2.2)