The size field listed in the Java Cache Viewer is not an accurate size for either jnlp applications or resources.
The code uses the CacheEntry.getContentSize(), which unless the item was downloaded using jardiff, is the actual urlconnection content size field, instead of the size of the file stored on disk.
for example, clear the cache, and run the simple 3d demo:
http://oklahoma.east/jnlp-servlet/deployment/javaws/generic/3d/hello.jnlp

the total cache size is 2919 K
the total size of the listed resources is 2762 K
the size of the one app is: 2596 K

these numbers should be a lot closer to equal.