[darwinbuild-dev] Project Version Numbers

After working with the diff plugin of darwinxref I notices that some project version numbers decrease. Is this normal? Did Apple really go to an older release when they upgraded the OS? An example is between build 8I127 and 8I1119. AppleFileSystemDriver differs: 7 vs 5 There are others, but this illustrates the question. So, can we assume that hiring version numbers are newer projects? Does Apple release order version of packages when they upgrade the OS? Are these mistakes in the plists? Michael